diff --git a/scheme/ikarus.apply.ss b/scheme/ikarus.apply.ss
index 22a5249..fd74208 100644
--- a/scheme/ikarus.apply.ss
+++ b/scheme/ikarus.apply.ss
@@ -10,8 +10,8 @@
     (let ()
       (define (err f ls)
         (if (procedure? f)
-            (error 'apply "not a list")
-            (error 'apply "~s is not a procedure" f)))
+            (error 'apply "not a list" ls)
+            (error 'apply "not a procedure" f)))
       (define (fixandgo f a0 a1 ls p d)
         (cond
           [(null? ($cdr d))
diff --git a/scheme/ikarus.boot.orig b/scheme/ikarus.boot.orig
index 931db26..303e0fa 100644
Binary files a/scheme/ikarus.boot.orig and b/scheme/ikarus.boot.orig differ
diff --git a/scheme/ikarus.bytevectors.ss b/scheme/ikarus.bytevectors.ss
index e37b52b..63fe562 100644
--- a/scheme/ikarus.bytevectors.ss
+++ b/scheme/ikarus.bytevectors.ss
@@ -56,18 +56,18 @@
       [(k) 
        (if (and (fixnum? k) ($fx>= k 0))
            ($make-bytevector k)
-           (error 'make-bytevector "~s is not a valid size" k))]
+           (error 'make-bytevector "not a valid size" k))]
       [(k fill)
        (if (and (fixnum? fill) ($fx<= -128 fill) ($fx<= fill 255))
            ($bytevector-fill (make-bytevector k) 0 k fill)
-           (error 'make-bytevector "~s is not a valid fill" fill))]))
+           (error 'make-bytevector "not a valid fill" fill))]))
 
   (define bytevector-fill!
     (lambda (x fill)
       (unless (bytevector? x)
-        (error 'bytevector-fill! "~s is not a bytevector" x))
+        (error 'bytevector-fill! "not a bytevector" x))
       (unless (and (fixnum? fill) ($fx<= -128 fill) ($fx<= fill 255))
-        (error 'bytevector-fill! "~s is not a valid fill" fill))
+        (error 'bytevector-fill! "not a valid fill" fill))
       ($bytevector-fill x 0 ($bytevector-length x) fill)))
 
 
@@ -75,23 +75,23 @@
     (lambda (x)
       (if (bytevector? x)
           ($bytevector-length x)
-          (error 'bytevector-length "~s is not a bytevector" x))))
+          (error 'bytevector-length "not a bytevector" x))))
 
   (define bytevector-s8-ref
     (lambda (x i)
       (if (bytevector? x)
           (if (and (fixnum? i) ($fx<= 0 i) ($fx< i ($bytevector-length x)))
               ($bytevector-s8-ref x i)
-              (error 'bytevector-s8-ref "invalid index ~s for ~s" i x))
-          (error 'bytevector-s8-ref "~s is not a bytevector" x))))
+              (error 'bytevector-s8-ref "invalid index" i x))
+          (error 'bytevector-s8-ref "not a bytevector" x))))
 
   (define bytevector-u8-ref
     (lambda (x i)
       (if (bytevector? x)
           (if (and (fixnum? i) ($fx<= 0 i) ($fx< i ($bytevector-length x)))
               ($bytevector-u8-ref x i)
-              (error 'bytevector-u8-ref "invalid index ~s for ~s" i x))
-          (error 'bytevector-u8-ref "~s is not a bytevector" x))))
+              (error 'bytevector-u8-ref "invalid index" i x))
+          (error 'bytevector-u8-ref "not a bytevector" x))))
 
 
   (define bytevector-s8-set!
@@ -100,9 +100,9 @@
           (if (and (fixnum? i) ($fx<= 0 i) ($fx< i ($bytevector-length x)))
               (if (and (fixnum? v) ($fx<= -128 v) ($fx<= v 127)) 
                   ($bytevector-set! x i v)
-                  (error 'bytevector-s8-set! "~s is not a byte" v))
-              (error 'bytevector-s8-set! "invalid index ~s for ~s" i x))
-          (error 'bytevector-s8-set! "~s is not a bytevector" x))))
+                  (error 'bytevector-s8-set! "not a byte" v))
+              (error 'bytevector-s8-set! "invalid index" i x))
+          (error 'bytevector-s8-set! "not a bytevector" x))))
   
   (define bytevector-u8-set!
     (lambda (x i v)
@@ -110,9 +110,9 @@
           (if (and (fixnum? i) ($fx<= 0 i) ($fx< i ($bytevector-length x)))
               (if (and (fixnum? v) ($fx<= 0 v) ($fx<= v 255))
                   ($bytevector-set! x i v)
-                  (error 'bytevector-u8-set! "~s is not an octet" v))
-              (error 'bytevector-u8-set! "invalid index ~s for ~s" i x))
-          (error 'bytevector-u8-set! "~s is not a bytevector" x))))
+                  (error 'bytevector-u8-set! "not an octet" v))
+              (error 'bytevector-u8-set! "invalid index" i x))
+          (error 'bytevector-u8-set! "not a bytevector" x))))
 
   (define bytevector-u16-native-ref ;;; HARDCODED
     (lambda (x i) 
@@ -124,8 +124,8 @@
               ($fxlogor
                 ($fxsll ($bytevector-u8-ref x i) 8)
                 ($bytevector-u8-ref x ($fxadd1 i)))
-              (error 'bytevector-u16-native-ref "invalid index ~s" i))
-          (error 'bytevector-u16-native-ref "~s is not a bytevector" x))))
+              (error 'bytevector-u16-native-ref "invalid index" i))
+          (error 'bytevector-u16-native-ref "not a bytevector" x))))
 
   
   (define bytevector-u16-native-set! ;;; HARDCODED
@@ -141,9 +141,9 @@
                   (begin
                     ($bytevector-set! x i ($fxsra n 8)) 
                     ($bytevector-set! x ($fxadd1 i) n))
-                  (error 'bytevector-u16-native-set! "invalid index ~s" i))
-              (error 'bytevector-u16-native-set! "invalid value ~s" n))
-          (error 'bytevector-u16-native-set! "~s is not a bytevector" x))))
+                  (error 'bytevector-u16-native-set! "invalid index" i))
+              (error 'bytevector-u16-native-set! "invalid value" n))
+          (error 'bytevector-u16-native-set! "not a bytevector" x))))
 
   (define bytevector-s16-native-set! ;;; HARDCODED
     (lambda (x i n) 
@@ -158,9 +158,9 @@
                   (begin
                     ($bytevector-set! x i ($fxsra n 8)) 
                     ($bytevector-set! x ($fxadd1 i) n))
-                  (error 'bytevector-s16-native-set! "invalid index ~s" i))
-              (error 'bytevector-s16-native-set! "invalid value ~s" n))
-          (error 'bytevector-s16-native-set! "~s is not a bytevector" x))))
+                  (error 'bytevector-s16-native-set! "invalid index" i))
+              (error 'bytevector-s16-native-set! "invalid value" n))
+          (error 'bytevector-s16-native-set! "not a bytevector" x))))
 
   (define bytevector-s16-native-ref ;;; HARDCODED
     (lambda (x i) 
@@ -172,8 +172,8 @@
               ($fxlogor
                 ($fxsll ($bytevector-s8-ref x i) 8)
                 ($bytevector-u8-ref x ($fxadd1 i)))
-              (error 'bytevector-s16-native-ref "invalid index ~s" i))
-          (error 'bytevector-s16-native-ref "~s is not a bytevector" x))))
+              (error 'bytevector-s16-native-ref "invalid index" i))
+          (error 'bytevector-s16-native-ref "not a bytevector" x))))
 
   (define bytevector-u16-ref
     (lambda (x i end) 
@@ -190,9 +190,9 @@
                  ($fxlogor
                    ($fxsll ($bytevector-u8-ref x (fxadd1 i)) 8)
                    ($bytevector-u8-ref x i))]
-                [else (error 'bytevector-u16-ref "invalid endianness ~s" end)])
-              (error 'bytevector-u16-ref "invalid index ~s" i))
-          (error 'bytevector-u16-ref "~s is not a bytevector" x))))
+                [else (error 'bytevector-u16-ref "invalid endianness" end)])
+              (error 'bytevector-u16-ref "invalid index" i))
+          (error 'bytevector-u16-ref "not a bytevector" x))))
 
   (define bytevector-u32-ref
     (lambda (x i end) 
@@ -215,9 +215,9 @@
                       ($fxlogor
                         ($fxsll ($bytevector-u8-ref x ($fx+ i 1)) 8)
                         ($bytevector-u8-ref x i))))]
-                [else (error 'bytevector-u32-ref "invalid endianness ~s" end)])
-              (error 'bytevector-u32-ref "invalid index ~s" i))
-          (error 'bytevector-u32-ref "~s is not a bytevector" x))))
+                [else (error 'bytevector-u32-ref "invalid endianness" end)])
+              (error 'bytevector-u32-ref "invalid index" i))
+          (error 'bytevector-u32-ref "not a bytevector" x))))
 
   (define bytevector-u32-native-ref
     (lambda (x i) 
@@ -232,8 +232,8 @@
                    ($fxlogor 
                      ($fxsll ($bytevector-u8-ref x ($fx+ i 2)) 8)
                      ($bytevector-u8-ref x ($fx+ i 3)))))
-              (error 'bytevector-u32-native-ref "invalid index ~s" i))
-          (error 'bytevector-u32-native-ref "~s is not a bytevector" x))))
+              (error 'bytevector-u32-native-ref "invalid index" i))
+          (error 'bytevector-u32-native-ref "not a bytevector" x))))
 
   (define bytevector-s32-ref
     (lambda (x i end) 
@@ -256,9 +256,9 @@
                       ($fxlogor
                         ($fxsll ($bytevector-u8-ref x ($fx+ i 1)) 8)
                         ($bytevector-u8-ref x i))))]
-                [else (error 'bytevector-s32-ref "invalid endianness ~s" end)])
-              (error 'bytevector-s32-ref "invalid index ~s" i))
-          (error 'bytevector-s32-ref "~s is not a bytevector" x))))
+                [else (error 'bytevector-s32-ref "invalid endianness" end)])
+              (error 'bytevector-s32-ref "invalid index" i))
+          (error 'bytevector-s32-ref "not a bytevector" x))))
 
   (define bytevector-s32-native-ref
     (lambda (x i) 
@@ -273,8 +273,8 @@
                    ($fxlogor 
                      ($fxsll ($bytevector-u8-ref x ($fx+ i 2)) 8)
                      ($bytevector-u8-ref x ($fx+ i 3)))))
-              (error 'bytevector-s32-native-ref "invalid index ~s" i))
-          (error 'bytevector-s32-native-ref "~s is not a bytevector" x))))
+              (error 'bytevector-s32-native-ref "invalid index" i))
+          (error 'bytevector-s32-native-ref "not a bytevector" x))))
 
   (define bytevector-u16-set!
     (lambda (x i n end) 
@@ -292,10 +292,10 @@
                     [(little) 
                      ($bytevector-set! x i n)
                      ($bytevector-set! x ($fxadd1 i) (fxsra n 8))]
-                    [else (error 'bytevector-u16-ref "invalid endianness ~s" end)])
-                  (error 'bytevector-u16-set! "invalid index ~s" i))
-              (error 'bytevector-u16-set! "invalid value ~s" n))
-          (error 'bytevector-u16-set! "~s is not a bytevector" x))))
+                    [else (error 'bytevector-u16-ref "invalid endianness" end)])
+                  (error 'bytevector-u16-set! "invalid index" i))
+              (error 'bytevector-u16-set! "invalid value" n))
+          (error 'bytevector-u16-set! "not a bytevector" x))))
 
 
   (define bytevector-u32-set!
@@ -324,10 +324,10 @@
                      (let ([b (logand n #xFFFF)])
                        ($bytevector-set! x ($fx+ i 1) ($fxsra b 8))
                        ($bytevector-set! x i b))]
-                    [else (error 'bytevector-u32-ref "invalid endianness ~s" end)])
-                  (error 'bytevector-u32-set! "invalid index ~s" i))
-              (error 'bytevector-u32-set! "invalid value ~s" n))
-          (error 'bytevector-u32-set! "~s is not a bytevector" x))))
+                    [else (error 'bytevector-u32-ref "invalid endianness" end)])
+                  (error 'bytevector-u32-set! "invalid index" i))
+              (error 'bytevector-u32-set! "invalid value" n))
+          (error 'bytevector-u32-set! "not a bytevector" x))))
 
   (define bytevector-u32-native-set!
     (lambda (x i n) 
@@ -348,9 +348,9 @@
                     (let ([b (logand n #xFFFF)])
                       ($bytevector-set! x ($fx+ i 2) ($fxsra b 8))
                       ($bytevector-set! x ($fx+ i 3) b)))
-                  (error 'bytevector-u32-native-set! "invalid index ~s" i))
-              (error 'bytevector-u32-native-set! "invalid value ~s" n))
-          (error 'bytevector-u32-native-set! "~s is not a bytevector" x))))
+                  (error 'bytevector-u32-native-set! "invalid index" i))
+              (error 'bytevector-u32-native-set! "invalid value" n))
+          (error 'bytevector-u32-native-set! "not a bytevector" x))))
 
 
   (define bytevector-s32-native-set!
@@ -372,9 +372,9 @@
                     (let ([b (logand n #xFFFF)])
                       ($bytevector-set! x ($fx+ i 2) ($fxsra b 8))
                       ($bytevector-set! x ($fx+ i 3) b)))
-                  (error 'bytevector-s32-native-set! "invalid index ~s" i))
-              (error 'bytevector-s32-native-set! "invalid value ~s" n))
-          (error 'bytevector-s32-native-set! "~s is not a bytevector" x))))
+                  (error 'bytevector-s32-native-set! "invalid index" i))
+              (error 'bytevector-s32-native-set! "invalid value" n))
+          (error 'bytevector-s32-native-set! "not a bytevector" x))))
 
   (define bytevector-s32-set!
     (lambda (x i n end) 
@@ -402,10 +402,10 @@
                      (let ([b (logand n #xFFFF)])
                        ($bytevector-set! x ($fx+ i 1) ($fxsra b 8))
                        ($bytevector-set! x i b))]
-                    [else (error 'bytevector-s32-ref "invalid endianness ~s" end)])
-                  (error 'bytevector-s32-set! "invalid index ~s" i))
-              (error 'bytevector-s32-set! "invalid value ~s" n))
-          (error 'bytevector-s32-set! "~s is not a bytevector" x))))
+                    [else (error 'bytevector-s32-ref "invalid endianness" end)])
+                  (error 'bytevector-s32-set! "invalid index" i))
+              (error 'bytevector-s32-set! "invalid value" n))
+          (error 'bytevector-s32-set! "not a bytevector" x))))
 
   (define bytevector-s16-ref
     (lambda (x i end) 
@@ -422,9 +422,9 @@
                  ($fxlogor
                    ($fxsll ($bytevector-s8-ref x (fxadd1 i)) 8)
                    ($bytevector-u8-ref x i))]
-                [else (error 'bytevector-s16-ref "invalid endianness ~s" end)])
-              (error 'bytevector-s16-ref "invalid index ~s" i))
-          (error 'bytevector-s16-ref "~s is not a bytevector" x))))
+                [else (error 'bytevector-s16-ref "invalid endianness" end)])
+              (error 'bytevector-s16-ref "invalid index" i))
+          (error 'bytevector-s16-ref "not a bytevector" x))))
 
 
   (define bytevector-s16-set!
@@ -443,10 +443,10 @@
                     [(little) 
                      ($bytevector-set! x i n)
                      ($bytevector-set! x ($fxadd1 i) (fxsra n 8))]
-                    [else (error 'bytevector-s16-ref "invalid endianness ~s" end)])
-                  (error 'bytevector-s16-set! "invalid index ~s" i))
-              (error 'bytevector-s16-set! "invalid value ~s" n))
-          (error 'bytevector-s16-set! "~s is not a bytevector" x))))
+                    [else (error 'bytevector-s16-ref "invalid endianness" end)])
+                  (error 'bytevector-s16-set! "invalid index" i))
+              (error 'bytevector-s16-set! "invalid value" n))
+          (error 'bytevector-s16-set! "not a bytevector" x))))
 
 
 
@@ -456,7 +456,7 @@
   (define bytevector->u8-list
     (lambda (x)
       (unless (bytevector? x)
-        (error 'bytevector->u8-list "~s is not a bytevector" x))
+        (error 'bytevector->u8-list "not a bytevector" x))
       (let f ([x x] [i ($bytevector-length x)] [ac '()])
         (cond
           [($fx= i 0) ac]
@@ -472,13 +472,13 @@
                       (if (pair? h)
                           (if (not (eq? h t))
                               (race ($cdr h) ($cdr t) ls ($fx+ n 2))
-                              (error 'u8-list->bytevector "circular list ~s" ls))
+                              (error 'u8-list->bytevector "circular list" ls))
                           (if (null? h)
                               ($fx+ n 1)
-                              (error 'u8-list->bytevector "~s is not a proper list" ls))))
+                              (error 'u8-list->bytevector "not a proper list" ls))))
                    (if (null? h)
                        n
-                       (error 'u8-list->bytevector "~s is not a proper list" ls))))]
+                       (error 'u8-list->bytevector "not a proper list" ls))))]
               [fill
                (lambda (s i ls)
                  (cond
@@ -486,7 +486,7 @@
                    [else
                     (let ([c ($car ls)])
                       (unless (and (fixnum? c) ($fx<= 0 c) ($fx<= c 255))
-                        (error 'u8-list->bytevector "~s is not an octet" c))
+                        (error 'u8-list->bytevector "not an octet" c))
                       ($bytevector-set! s i c)
                       (fill s ($fxadd1 i) (cdr ls)))]))])
        (lambda (ls)
@@ -498,7 +498,7 @@
   (define bytevector-copy
     (lambda (src)
       (unless (bytevector? src)
-        (error 'bytevector-copy "~s is not a bytevector" src))
+        (error 'bytevector-copy "not a bytevector" src))
       (let ([n ($bytevector-length src)])
         (let f ([src src] [dst ($make-bytevector n)] [i 0] [n n])
           (cond
@@ -510,9 +510,9 @@
   (define bytevector=? 
     (lambda (x y)
       (unless (bytevector? x)
-        (error 'bytevector=? "~s is not a bytevector" x))
+        (error 'bytevector=? "not a bytevector" x))
       (unless (bytevector? y)
-        (error 'bytevector=? "~s is not a bytevector" y))
+        (error 'bytevector=? "not a bytevector" y))
       (let ([n ($bytevector-length x)])
         (and ($fx= n ($bytevector-length y))
              (let f ([x x] [y y] [i 0] [n n])
@@ -525,21 +525,21 @@
     (lambda (src src-start dst dst-start k) 
       (cond
         [(or (not (fixnum? src-start)) ($fx< src-start 0))
-         (error 'bytevector-copy! "~s is not a valid starting index" src-start)]
+         (error 'bytevector-copy! "not a valid starting index" src-start)]
         [(or (not (fixnum? dst-start)) ($fx< dst-start 0))
-         (error 'bytevector-copy! "~s is not a valid starting index" dst-start)]
+         (error 'bytevector-copy! "not a valid starting index" dst-start)]
         [(or (not (fixnum? k)) ($fx< k 0))
-         (error 'bytevector-copy! "~s is not a valid length" k)]
+         (error 'bytevector-copy! "not a valid length" k)]
         [(not (bytevector? src)) 
-         (error 'bytevector-copy! "~s is not a bytevector" src)]
+         (error 'bytevector-copy! "not a bytevector" src)]
         [(not (bytevector? dst)) 
-         (error 'bytevector-copy! "~s is not a bytevector" dst)]
+         (error 'bytevector-copy! "not a bytevector" dst)]
         [(let ([n ($fx+ src-start k)])
            (or ($fx< n 0) ($fx>= n ($bytevector-length src))))
-         (error 'bytevector-copy! "~s+~s is out of range" src-start k)]
+         (error 'bytevector-copy! "out of range" src-start k)]
         [(let ([n ($fx+ dst-start k)])
            (or ($fx< n 0) ($fx>= n ($bytevector-length dst))))
-         (error 'bytevector-copy! "~s+~s is out of range" dst-start k)]
+         (error 'bytevector-copy! "out of range" dst-start k)]
         [(eq? src dst)
          (cond
            [($fx< dst-start src-start)
@@ -647,33 +647,33 @@
     (define bytevector-sint-ref
       (lambda (x k endianness size)
         (define who 'bytevector-sint-ref)
-        (unless (bytevector? x) (error who "~s is not a bytevector" x))
-        (unless (and (fixnum? k) ($fx>= k 0)) (error who "invalid index ~s" k))
-        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size ~s" size))
+        (unless (bytevector? x) (error who "not a bytevector" x))
+        (unless (and (fixnum? k) ($fx>= k 0)) (error who "invalid index" k))
+        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size" size))
         (let ([n ($bytevector-length x)])
-          (unless ($fx< k n) (error who "index ~s is out of range" k))
+          (unless ($fx< k n) (error who "index is out of range" k))
           (let ([end ($fx+ k size)])
             (unless (and ($fx>= end 0) ($fx<= end n))
-              (error who "~s+~s is out of range" k size))
+              (error who "out of range" k size))
             (case endianness
               [(little) (sref-little x k end)]
               [(big)    (sref-big x k end)]
-              [else (error who "invalid endianness ~s" endianness)])))))
+              [else (error who "invalid endianness" endianness)])))))
     (define bytevector-uint-ref
       (lambda (x k endianness size)
         (define who 'bytevector-uint-ref)
-        (unless (bytevector? x) (error who "~s is not a bytevector" x))
-        (unless (and (fixnum? k) ($fx>= k 0)) (error who "invalid index ~s" k))
-        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size ~s" size))
+        (unless (bytevector? x) (error who "not a bytevector" x))
+        (unless (and (fixnum? k) ($fx>= k 0)) (error who "invalid index" k))
+        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size" size))
         (let ([n ($bytevector-length x)])
-          (unless ($fx< k n) (error who "index ~s is out of range" k))
+          (unless ($fx< k n) (error who "index is out of range" k))
           (let ([end ($fx+ k size)])
             (unless (and ($fx>= end 0) ($fx<= end n))
-              (error who "~s+~s is out of range" k size))
+              (error who "out of range" k size))
             (case endianness
               [(little) (uref-little x k end)]
               [(big)    (uref-big x k end)]
-              [else (error who "invalid endianness ~s" endianness)])))))
+              [else (error who "invalid endianness" endianness)])))))
     (define (bytevector->some-list x k n ls proc who)
       (cond
         [($fx= n 0) ls]
@@ -683,36 +683,36 @@
              [($fx>= i 0)
               (bytevector->some-list x k i (cons (proc x i n) ls) proc who)]
              [else
-              (error who "invalid size ~s" k)]))]))
+              (error who "invalid size" k)]))]))
     (define bytevector->uint-list
       (lambda (x endianness size)
         (define who 'bytevector->uint-list)
-        (unless (bytevector? x) (error who "~s is not a bytevector" x))
-        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size ~s" size))
+        (unless (bytevector? x) (error who "not a bytevector" x))
+        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size" size))
         (case endianness
           [(little) (bytevector->some-list x size ($bytevector-length x)
                       '() uref-little 'bytevector->uint-list)]
           [(big)    (bytevector->some-list x size ($bytevector-length x) 
                       '() uref-big 'bytevector->uint-list)]
-          [else (error who "invalid endianness ~s" endianness)])))
+          [else (error who "invalid endianness" endianness)])))
     (define bytevector->sint-list
       (lambda (x endianness size)
         (define who 'bytevector->sint-list)
-        (unless (bytevector? x) (error who "~s is not a bytevector" x))
-        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size ~s" size))
+        (unless (bytevector? x) (error who "not a bytevector" x))
+        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size" size))
         (case endianness
           [(little) (bytevector->some-list x size ($bytevector-length x)
                       '() sref-little 'bytevector->sint-list)]
           [(big)    (bytevector->some-list x size ($bytevector-length x) 
                       '() sref-big 'bytevector->sint-list)]
-          [else (error who "invalid endianness ~s" endianness)]))))
+          [else (error who "invalid endianness" endianness)]))))
 
   (module (bytevector-uint-set! bytevector-sint-set!)
     (define (lufx-set! x k1 n k2 who no)
       (cond
         [($fx= k1 k2) 
          (unless ($fxzero? n)
-           (error who "number ~s does not fit" no))]
+           (error who "number does not fit" no))]
         [else
          (lufx-set! x ($fxadd1 k1) ($fxsra n 8) k2 who no)
          ($bytevector-set! x k1 ($fxlogand n 255))]))
@@ -720,7 +720,7 @@
       (cond
         [($fx= k1 k2) 
          (unless ($fx= n -1) ;;; BUG: does not catch all errors
-           (error who "number ~s does not fit" no))]
+           (error who "number does not fit" no))]
         [else
          (lsfx-set! x ($fxadd1 k1) ($fxsra n 8) k2 who no)
          ($bytevector-set! x k1 ($fxlogand n 255))]))
@@ -728,7 +728,7 @@
       (cond
         [($fx= k1 k2) 
          (unless ($fxzero? n)
-           (error who "number ~s does not fit" no))]
+           (error who "number does not fit" no))]
         [else
          (let ([k2 ($fxsub1 k2)])
            (bufx-set! x k1 ($fxsra n 8) k2 who no)
@@ -737,7 +737,7 @@
       (cond
         [($fx= k1 k2) 
          (unless ($fx= n -1)
-           (error who "number ~s does not fit" no))]
+           (error who "number does not fit" no))]
         [else
          (let ([k2 ($fxsub1 k2)])
            (bsfx-set! x k1 ($fxsra n 8) k2 who no)
@@ -765,8 +765,8 @@
              [(#x00) ;;; borrow is 0, last byte was positive
               (if ($fx< xi xj)
                   (bv-neg-zero! x xi xj)
-                  (error who "number ~s does not fit" n))]
-             [else (error 'lbn-neg-copy! "BUG: not handled ~s" c)])]
+                  (error who "number does not fit" n))]
+             [else (error 'lbn-neg-copy! "BUG: not handled" c)])]
           [else
            (let ([c ($fx- ($fx+ 255 ($fxsra c 8)) ($bignum-byte-ref n ni))])
              (lbn-neg-copy! x ($fxadd1 xi) n ($fxadd1 ni) xj nj c)
@@ -782,8 +782,8 @@
              [(#x00) ;;; borrow is 0, last byte was positive
               (if ($fx< xi xj)
                   (bv-neg-zero! x xi xj)
-                  (error who "number ~s does not fit" n))]
-             [else (error 'bbn-neg-copy! "BUG: not handled ~s" c)])]
+                  (error who "number does not fit" n))]
+             [else (error 'bbn-neg-copy! "BUG: not handled" c)])]
           [else
            (let ([c ($fx- ($fx+ 255 ($fxsra c 8)) ($bignum-byte-ref n ni))]
                  [xj ($fxsub1 xj)])
@@ -799,7 +799,7 @@
               ;;; last byte was positive
               (bv-zero! x xi xj)]
              [else 
-              (error who "number ~s does not fit" n)])]
+              (error who "number does not fit" n)])]
           [else
            (let ([c ($bignum-byte-ref n ni)])
              (lbn-pos-copy! x ($fxadd1 xi) n ($fxadd1 ni) nj xj c)
@@ -814,7 +814,7 @@
               ;;; last byte was positive
               (bv-zero! x xi xj)]
              [else 
-              (error who "number ~s does not fit" n)])]
+              (error who "number does not fit" n)])]
           [else
            (let ([c ($bignum-byte-ref n ni)]
                  [xj ($fxsub1 xj)])
@@ -842,9 +842,9 @@
               i))))
     (define (make-bytevector-uint-set! who)
       (lambda (x k n endianness size)
-        (unless (bytevector? x) (error who "~s is not a bytevector" x))
-        (unless (and (fixnum? k) ($fx>= k 0)) (error who "invalid index ~s" k))
-        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size ~s" size))
+        (unless (bytevector? x) (error who "not a bytevector" x))
+        (unless (and (fixnum? k) ($fx>= k 0)) (error who "invalid index" k))
+        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size" size))
         (case endianness
           [(little)
            (cond
@@ -858,9 +858,9 @@
                       [($fx< sz size)
                        (lbn-copy! x k n 0 sz)
                        (bv-zero! x ($fx+ k sz) ($fx+ k size))]
-                      [else (error who "number ~s does not fit" n)]))
-                  (error who "value ~s must be positive" n))]
-             [else (error who "invalid value argument ~s" n)])]
+                      [else (error who "number does not fit" n)]))
+                  (error who "value must be positive" n))]
+             [else (error who "invalid value argument" n)])]
           [(big)
            (cond
              [(fixnum? n) (bufx-set! x k n ($fx+ k size) who n)]
@@ -873,10 +873,10 @@
                       [($fx< sz size)
                        (bbn-copy! x ($fx+ k size) n 0 sz)
                        (bv-zero! x k ($fx+ k ($fx- size sz)))]
-                      [else (error who "number ~s does not fit" n)]))
-                  (error who "value ~s must be positive" n))]
-             [else (error who "invalid value argument ~s" n)])]
-          [else (error who "invalid endianness ~s" endianness)])))
+                      [else (error who "number does not fit" n)]))
+                  (error who "value must be positive" n))]
+             [else (error who "invalid value argument" n)])]
+          [else (error who "invalid endianness" endianness)])))
     (define bytevector-uint-set! (make-bytevector-uint-set! 'bytevector-uint-set!))
     (define (make-bytevector-sint-set! who)
       (define bbn-neg-copy! (make-bbn-neg-copy! who))
@@ -884,9 +884,9 @@
       (define lbn-neg-copy! (make-lbn-neg-copy! who))
       (define lbn-pos-copy! (make-lbn-pos-copy! who))
       (lambda (x k n endianness size)
-        (unless (bytevector? x) (error who "~s is not a bytevector" x))
-        (unless (and (fixnum? k) ($fx>= k 0)) (error who "invalid index ~s" k))
-        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size ~s" size))
+        (unless (bytevector? x) (error who "not a bytevector" x))
+        (unless (and (fixnum? k) ($fx>= k 0)) (error who "invalid index" k))
+        (unless (and (fixnum? size) ($fx>= size 1)) (error who "invalid size" size))
         (case endianness
           [(little)
            (cond
@@ -897,13 +897,13 @@
                     (cond
                       [($fx<= sz size) 
                        (lbn-pos-copy! x k n 0 size sz 255)]
-                      [else (error who "number ~s does not fit" n)]))
+                      [else (error who "number does not fit" n)]))
                   (let ([sz (bignum-bytes n)])
                     (cond
                       [($fx<= sz size) 
                        (lbn-neg-copy! x k n 0 size sz 256)]
-                      [else (error who "number ~s does not fit" n)])))]
-             [else (error who "invalid value argument ~s" n)])]
+                      [else (error who "number does not fit" n)])))]
+             [else (error who "invalid value argument" n)])]
           [(big)
            (cond
              [(fixnum? n) (bsfx-set! x k n ($fx+ k size) who n)]
@@ -913,14 +913,14 @@
                     (cond
                       [($fx<= sz size) 
                        (bbn-pos-copy! x k n 0 size sz 255)]
-                      [else (error who "number ~s does not fit" n)]))
+                      [else (error who "number does not fit" n)]))
                   (let ([sz (bignum-bytes n)])
                     (cond
                       [($fx<= sz size) 
                        (bbn-neg-copy! x k n 0 size sz 256)]
-                      [else (error who "number ~s does not fit" n)])))] 
-             [else (error who "invalid value argument ~s" n)])]
-          [else (error who "invalid endianness ~s" endianness)])))
+                      [else (error who "number does not fit" n)])))] 
+             [else (error who "invalid value argument" n)])]
+          [else (error who "invalid endianness" endianness)])))
     (define bytevector-sint-set! (make-bytevector-sint-set! 'bytevector-sint-set!)))
 
   (module (uint-list->bytevector sint-list->bytevector)
@@ -936,15 +936,15 @@
                          (bv-set! bv idx a endianness size)
                          (bv-set! bv ($fx+ idx size) ($car h) endianness size)
                          bv)
-                       (error who "circular list ~s" ls))
+                       (error who "circular list" ls))
                    (if (null? h)
                        (let ([bv (make-bytevector ($fx+ idx size))])
                          (bv-set! bv idx a endianness size)
                          bv)
-                       (error who "~s is not a proper list" ls))))
+                       (error who "not a proper list" ls))))
             (if (null? h)
                 (make-bytevector idx)
-                (error who "~s is not a proper list" ls))))
+                (error who "not a proper list" ls))))
       (lambda (ls endianness size)
         (race ls ls ls 0 endianness size)))
     (define uint-list->bytevector 
diff --git a/scheme/ikarus.cafe.ss b/scheme/ikarus.cafe.ss
index 50e7911..f180f13 100644
--- a/scheme/ikarus.cafe.ss
+++ b/scheme/ikarus.cafe.ss
@@ -97,7 +97,7 @@ description:
       [() (do-new-cafe default-cafe-eval)]
       [(p)
        (unless (procedure? p)
-         (error 'new-cafe "~s is not a procedure" p))
+         (error 'new-cafe "not a procedure" p))
        (do-new-cafe p)]))
   )
 
diff --git a/scheme/ikarus.chars.ss b/scheme/ikarus.chars.ss
index d2e3cf3..3d2f2c2 100644
--- a/scheme/ikarus.chars.ss
+++ b/scheme/ikarus.chars.ss
@@ -11,26 +11,26 @@
   (define integer->char
     (lambda (n)
       (cond
-        [(not (fixnum? n)) (error 'integer->char "invalid argument ~s" n)]
-        [($fx< n 0) (error 'integer->char "~s is negative" n)]
+        [(not (fixnum? n)) (error 'integer->char "invalid argument" n)]
+        [($fx< n 0) (error 'integer->char "negative" n)]
         [($fx<= n #xD7FF) ($fixnum->char n)]
         [($fx< n #xE000)
-         (error 'integer->char "~s does not have a unicode representation" n)]
+         (error 'integer->char "integer does not have a unicode representation" n)]
         [($fx<= n #x10FFFF) ($fixnum->char n)]
         [else (error 'integer->char 
-                "~s does not have a unicode representation" n)])))
+                "integer does not have a unicode representation" n)])))
   
   (define char->integer 
     (lambda (x) 
       (unless (char? x)
-        (error 'char->integer "~s is not a character" x))
+        (error 'char->integer "not a character" x))
       ($char->fixnum x)))
 
   ;;; FIXME: this file is embarrasing
   (define char=?
     (let ()
       (define (err x)
-        (error 'char=? "~s is not a character" x))
+        (error 'char=? "not a character" x))
       (case-lambda
         [(c1 c2)
          (if (char? c1)
@@ -67,7 +67,7 @@
   (define char<?
     (let ()
       (define (err x)
-        (error 'char<? "~s is not a character" x))
+        (error 'char<? "not a character" x))
       (case-lambda
         [(c1 c2)
          (if (char? c1)
@@ -104,7 +104,7 @@
   (define char<=?
     (let ()
       (define (err x)
-        (error 'char<=? "~s is not a character" x))
+        (error 'char<=? "not a character" x))
       (case-lambda
         [(c1 c2)
          (if (char? c1)
@@ -141,7 +141,7 @@
   (define char>?
     (let ()
       (define (err x)
-        (error 'char>? "~s is not a character" x))
+        (error 'char>? "not a character" x))
       (case-lambda
         [(c1 c2)
          (if (char? c1)
@@ -178,7 +178,7 @@
   (define char>=?
     (let ()
       (define (err x)
-        (error 'char>=? "~s is not a character" x))
+        (error 'char>=? "not a character" x))
       (case-lambda
         [(c1 c2)
          (if (char? c1)
diff --git a/scheme/ikarus.code-objects.ss b/scheme/ikarus.code-objects.ss
index 5030465..96eaaf3 100644
--- a/scheme/ikarus.code-objects.ss
+++ b/scheme/ikarus.code-objects.ss
@@ -16,75 +16,75 @@
   (define make-code
     (lambda (code-size freevars)
       (unless (and (fixnum? code-size) ($fx>= code-size 0))
-        (error 'make-code "~s is not a valid code size" code-size))
+        (error 'make-code "not a valid code size" code-size))
       (unless (and (fixnum? freevars) ($fx>= freevars 0))
-        (error 'make-code "~s is not a valid number of free vars" freevars))
+        (error 'make-code "not a valid number of free vars" freevars))
       (foreign-call "ikrt_make_code" code-size freevars '#())))
 
   (define code-reloc-vector
     (lambda (x)
-      (unless (code? x) (error 'code-reloc-vector "~s is not a code" x))
+      (unless (code? x) (error 'code-reloc-vector "not a code" x))
       ($code-reloc-vector x)))
 
   (define code-freevars
     (lambda (x)
-      (unless (code? x) (error 'code-closure-size "~s is not a code" x))
+      (unless (code? x) (error 'code-closure-size "not a code" x))
       ($code-freevars x)))
 
   (define code-size
     (lambda (x)
-      (unless (code? x) (error 'code-size "~s is not a code" x))
+      (unless (code? x) (error 'code-size "not a code" x))
       ($code-size x)))
 
   (define code-set!
     (lambda (x i v)
-      (unless (code? x) (error 'code-set! "~s is not a code" x))
+      (unless (code? x) (error 'code-set! "not a code" x))
       (unless (and (fixnum? i)
                    ($fx>= i 0)
                    ($fx< i ($code-size x)))
-        (error 'code-set! "~s is not a valid index" i))
+        (error 'code-set! "not a valid index" i))
       (unless (and (fixnum? v)
                    ($fx>= v 0)
                    ($fx< v 256))
-        (error 'code-set! "~s is not a valid byte" v))
+        (error 'code-set! "not a valid byte" v))
       ($code-set! x i v)))
 
   (define code-ref
     (lambda (x i)
-      (unless (code? x) (error 'code-ref "~s is not a code" x))
+      (unless (code? x) (error 'code-ref "not a code" x))
       (unless (and (fixnum? i)
                    ($fx>= i 0)
                    ($fx< i ($code-size x)))
-        (error 'code-ref "~s is not a valid index" i))
+        (error 'code-ref "not a valid index" i))
       ($code-ref x i)))
 
   (define set-code-reloc-vector!
     (lambda (x v)
       (unless (code? x) 
-        (error 'set-code-reloc-vector! "~s is not a code" x))
+        (error 'set-code-reloc-vector! "not a code" x))
       (unless (vector? v)
-        (error 'set-code-reloc-vector! "~s is not a vector" v))
+        (error 'set-code-reloc-vector! "not a vector" v))
       (foreign-call "ikrt_set_code_reloc_vector" x v)))
 
 
   (define set-code-annotation!
     (lambda (x v)
       (unless (code? x) 
-        (error 'set-code-annotation! "~s is not a code" x))
+        (error 'set-code-annotation! "not a code" x))
       (foreign-call "ikrt_set_code_annotation" x v)))
 
   (define code->thunk
     (lambda (x)
       (unless (code? x)
-        (error 'code->thunk "~s is not a a code object" x))
+        (error 'code->thunk "not a a code object" x))
       (unless ($fxzero? ($code-freevars x))
-        (error 'code->thunk "~s has free variables" x))
+        (error 'code->thunk "has free variables" x))
       ($code->closure x)))
 
   (define (procedure-annotation x)
     (if (procedure? x) 
         ($code-annotation ($closure-code x))
-        (error 'procedure-annotation "~s is not a procedure" x)))
+        (error 'procedure-annotation "not a procedure" x)))
 
   )
 
diff --git a/scheme/ikarus.codecs.ss b/scheme/ikarus.codecs.ss
index 1637418..b886de2 100644
--- a/scheme/ikarus.codecs.ss
+++ b/scheme/ikarus.codecs.ss
@@ -46,17 +46,17 @@
   (define (codec->fixnum x who)
     (cond
       [(assq x codec-alist) => cdr]
-      [else (error who "~s is not a valid coded" x)]))
+      [else (error who "not a valid coded" x)]))
 
   (define (eol-style->fixnum x who)
     (cond
       [(assq x eol-style-alist) => cdr]
-      [else (error who "~s is not a valid eol-style" x)]))
+      [else (error who "not a valid eol-style" x)]))
 
   (define (error-handling-mode->fixnum x who)
     (cond
       [(assq x error-handling-mode-alist) => cdr]
-      [else (error who "~s is not a valid error-handling mode" x)]))
+      [else (error who "not a valid error-handling mode" x)]))
 
   (define make-transcoder
     (case-lambda
@@ -79,24 +79,24 @@
     (if ($transcoder? x) 
         (let ([tag (fxlogand ($transcoder->data x) codec-mask)])
           (or (rev-lookup tag codec-alist)
-              (error who "~s has no codec" x)))
-        (error who "~s is not a transcoder" x)))
+              (error who "transcoder has no codec" x)))
+        (error who "not a transcoder" x)))
 
   (define (transcoder-eol-style x) 
     (define who 'transcoder-eol-style)
     (if ($transcoder? x) 
         (let ([tag (fxlogand ($transcoder->data x) eol-style-mask)])
           (or (rev-lookup tag eol-style-alist)
-              (error who "~s has no eol-style" x)))
-        (error who "~s is not a transcoder" x)))
+              (error who "transcoder has no eol-style" x)))
+        (error who "not a transcoder" x)))
 
   (define (transcoder-error-handling-mode x) 
     (define who 'transcoder-error-handling-mode)
     (if ($transcoder? x) 
         (let ([tag (fxlogand ($transcoder->data x) error-handling-mode-mask)])
           (or (rev-lookup tag error-handling-mode-alist)
-              (error who "~s has no error-handling mode" x)))
-        (error who "~s is not a transcoder" x)))
+              (error who "transcoder has no error-handling mode" x)))
+        (error who "not a transcoder" x)))
 
   (define (buffer-mode? x)
     (and (memq x '(none line block)) #t))
@@ -118,7 +118,7 @@
       
   (define (file-options-spec ls)
     (unless (list? ls) 
-      (error 'file-options-spec "~s is not a list" ls))
+      (error 'file-options-spec "not a list" ls))
     (let f ([ls ls] [n 0])
       (cond
         [(null? ls) (vector-ref file-options-vec n)]
diff --git a/scheme/ikarus.compiler.altcogen.ss b/scheme/ikarus.compiler.altcogen.ss
index bf6b9c7..48f255d 100644
--- a/scheme/ikarus.compiler.altcogen.ss
+++ b/scheme/ikarus.compiler.altcogen.ss
@@ -29,25 +29,25 @@
   ;;;
   (define (check-gensym x)
     (unless (gensym? x)
-      (error who "invalid gensym ~s" x)))
+      (error who "invalid gensym" x)))
   ;;;
   (define (check-label x)
     (struct-case x
       [(code-loc label)
        (check-gensym label)]
-      [else (error who "invalid label ~s" x)]))
+      [else (error who "invalid label" x)]))
   ;;;
   (define (check-var x)
     (struct-case x 
       [(var) (void)]
-      [else (error who "invalid var ~s" x)]))
+      [else (error who "invalid var" x)]))
   ;;;
   (define (check-closure x)
     (struct-case x
       [(closure label free*)
        (check-label label)
        (for-each check-var free*)]
-      [else (error who "invalid closure ~s" x)]))
+      [else (error who "invalid closure" x)]))
   ;;;
   (define (mkfuncall op arg*)
     (import primops)
@@ -81,25 +81,25 @@
        (make-jmpcall label (Expr rator) (map Expr arg*))]
       [(mvcall rator k)
        (make-mvcall (Expr rator) (Clambda k))]
-      [else (error who "invalid expr ~s" x)]))
+      [else (error who "invalid expr" x)]))
   ;;;
   (define (ClambdaCase x)
     (struct-case x
       [(clambda-case info body)
        (make-clambda-case info (Expr body))]
-      [else (error who "invalid clambda-case ~s" x)]))
+      [else (error who "invalid clambda-case" x)]))
   ;;;
   (define (Clambda x)
     (struct-case x
       [(clambda label case* free* name)
        (make-clambda label (map ClambdaCase case*) free* name)]
-      [else (error who "invalid clambda ~s" x)]))
+      [else (error who "invalid clambda" x)]))
   ;;;
   (define (Program x)
     (struct-case x 
       [(codes code* body)
        (make-codes (map Clambda code*) (Expr body))]
-      [else (error who "invalid program ~s" x)]))
+      [else (error who "invalid program" x)]))
   ;;;
   (Program x))
 
@@ -150,7 +150,7 @@
          (make-jmpcall label (Expr rator) (map Expr arg*))]
         [(mvcall rator k)
          (make-mvcall (Expr rator) (Clambda k))]
-        [else (error who "invalid expr ~s" x)]))
+        [else (error who "invalid expr" x)]))
     Expr)
   ;;;
   (define (ClambdaCase free*)
@@ -163,20 +163,20 @@
               (make-clambda-case 
                 (make-case-info label (cons cp args) proper)
                 ((Expr cp free*) body)))])]
-        [else (error who "invalid clambda-case ~s" x)])))
+        [else (error who "invalid clambda-case" x)])))
   ;;;
   (define (Clambda x)
     (struct-case x
       [(clambda label case* free* name)
        (make-clambda label (map (ClambdaCase free*) case*) 
                      free* name)]
-      [else (error who "invalid clambda ~s" x)]))
+      [else (error who "invalid clambda" x)]))
   ;;;
   (define (Program x)
     (struct-case x 
       [(codes code* body)
        (make-codes (map Clambda code*) ((Expr #f '()) body))]
-      [else (error who "invalid program ~s" x)]))
+      [else (error who "invalid program" x)]))
   ;;;
   (Program x))
 
@@ -268,7 +268,7 @@
     [(assq x '([%eax 0] [%edi 1] [%ebx 2] [%edx 3] 
                [%ecx 4] [%esi 5] [%esp 6] [%ebp 7])) 
      => cadr]
-    [else (error 'register-index "~s is not a register" x)]))
+    [else (error 'register-index "not a register" x)]))
 
 
 (define non-8bit-registers '(%edi))
@@ -306,7 +306,7 @@
           (let ([t (unique-var 'tmp)])
             (do-bind (list t) (list x)
               (k t)))]
-         [else (error who "invalid S ~s" x)])]))
+         [else (error who "invalid S" x)])]))
   ;;;
   (define (do-bind lhs* rhs* body)
     (cond
@@ -452,7 +452,7 @@
                       (V d a)
                       (make-set ecx b)
                       (make-asm-instr op d ecx))))]))]
-         [else (error who "invalid value op ~s" op)])]
+         [else (error who "invalid value op" op)])]
       [(funcall rator rands) 
        (handle-nontail-call rator rands d #f)]
       [(jmpcall label rator rands) 
@@ -468,7 +468,7 @@
       [else 
        (if (symbol? x) 
            (make-set d x)
-           (error who "invalid value ~s" (unparse x)))]))
+           (error who "invalid value" (unparse x)))]))
   ;;;
   (define (assign* lhs* rhs* ac)
     (cond
@@ -506,7 +506,7 @@
               (lambda (s*)
                 (make-asm-instr op (car s*) (cadr s*))))]
          [(nop interrupt incr/zero?) x]
-         [else (error 'impose-effect "invalid instr ~s" x)])]
+         [else (error 'impose-effect "invalid instr" x)])]
       [(funcall rator rands)
        (handle-nontail-call rator rands #f #f)]
       [(jmpcall label rator rands) 
@@ -517,7 +517,7 @@
          rands #f op)]
       [(shortcut body handler)
        (make-shortcut (E body) (E handler))]
-      [else (error who "invalid effect ~s" x)]))
+      [else (error who "invalid effect" x)]))
   ;;; impose pred
   (define (P x)
     (struct-case x
@@ -541,7 +541,7 @@
                     (make-asm-instr op a b))))]))]
         [(shortcut body handler)
          (make-shortcut (P body) (P handler))]
-      [else (error who "invalid pred ~s" x)]))
+      [else (error who "invalid pred" x)]))
   ;;;
   (define (handle-tail-call target rator rands)
     (let* ([args (cons rator rands)]
@@ -624,7 +624,7 @@
       [(forcall) (VT x)]
       [(shortcut body handler)
        (make-shortcut (Tail body) (Tail handler))]
-      [else (error who "invalid tail ~s" x)]))
+      [else (error who "invalid tail" x)]))
   ;;;
   (define (formals-locations args)
     (let f ([regs parameter-registers] [args args])
@@ -707,21 +707,21 @@
 
   (define (make-empty-set) (make-set '()))
   (define (set-member? x s) 
-    ;(unless (fixnum? x) (error 'set-member? "~s is not a fixnum" x))
-    (unless (set? s) (error 'set-member? "~s is not a set" s))
+    ;(unless (fixnum? x) (error 'set-member? "not a fixnum" x))
+    (unless (set? s) (error 'set-member? "not a set" s))
     (memq x (set-v s)))
 
   (define (empty-set? s)
-    (unless (set? s) (error 'empty-set? "~s is not a set" s))
+    (unless (set? s) (error 'empty-set? "not a set" s))
     (null? (set-v s)))
     
   (define (set->list s)
-    (unless (set? s) (error 'set->list "~s is not a set" s))
+    (unless (set? s) (error 'set->list "not a set" s))
     (set-v s))
     
   (define (set-add x s)
-    ;(unless (fixnum? x) (error 'set-add "~s is not a fixnum" x))
-    (unless (set? s) (error 'set-add "~s is not a set" s))
+    ;(unless (fixnum? x) (error 'set-add "not a fixnum" x))
+    (unless (set? s) (error 'set-add "not a set" s))
     (cond
       [(memq x (set-v s)) s]
       [else (make-set (cons x (set-v s)))]))
@@ -733,8 +733,8 @@
       [else (cons (car s) (rem x (cdr s)))])) 
 
   (define (set-rem x s)
-    ;(unless (fixnum? x) (error 'set-rem "~s is not a fixnum" x))
-    (unless (set? s) (error 'set-rem "~s is not a set" s))
+    ;(unless (fixnum? x) (error 'set-rem "not a fixnum" x))
+    (unless (set? s) (error 'set-rem "not a set" s))
     (make-set (rem x (set-v s))))
   
   (define (difference s1 s2)
@@ -743,17 +743,17 @@
       [else (difference (rem (car s2) s1) (cdr s2))]))
 
   (define (set-difference s1 s2)
-    (unless (set? s1) (error 'set-difference "~s is not a set" s1))
-    (unless (set? s2) (error 'set-difference "~s is not a set" s2))
+    (unless (set? s1) (error 'set-difference "not a set" s1))
+    (unless (set? s2) (error 'set-difference "not a set" s2))
     (make-set (difference (set-v s1) (set-v s2))))
     
   (define (set-union s1 s2)
-    (unless (set? s1) (error 'set-union "~s is not a set" s1))
-    (unless (set? s2) (error 'set-union "~s is not a set" s2))
+    (unless (set? s1) (error 'set-union "not a set" s1))
+    (unless (set? s2) (error 'set-union "not a set" s2))
     (make-set (union (set-v s1) (set-v s2))))
 
   (define (list->set ls)
-    ;(unless (andmap fixnum? ls) (error 'set-rem "~s is not a list of fixnum" ls))
+    ;(unless (andmap fixnum? ls) (error 'set-rem "not a list of fixnum" ls))
     (make-set ls))
 
   (define (union s1 s2)
@@ -790,7 +790,7 @@
   (define (empty-set? s) (eqv? s 0))
   
   (define (set-member? n s) 
-    (unless (fixnum? n) (error 'set-member? "~s is not a fixnum" n))
+    (unless (fixnum? n) (error 'set-member? "not a fixnum" n))
     (let f ([s s] [i (index-of n)] [j (mask-of n)])
       (cond
         [(pair? s)
@@ -801,7 +801,7 @@
         [else #f])))
 
   (define (set-add n s)
-    (unless (fixnum? n) (error 'set-add "~s is not a fixnum" n))
+    (unless (fixnum? n) (error 'set-add "not a fixnum" n))
     (let f ([s s] [i (index-of n)] [j (mask-of n)])
       (cond
         [(pair? s)
@@ -824,7 +824,7 @@
         (cons a d)))
 
   (define (set-rem n s)
-    (unless (fixnum? n) (error 'set-rem "~s is not a fixnum" n))
+    (unless (fixnum? n) (error 'set-rem "not a fixnum" n))
     (let f ([s s] [i (index-of n)] [j (mask-of n)])
       (cond
         [(pair? s)
@@ -888,7 +888,7 @@
             (fxlogand s1 (fxlognot s2)))))
 
   (define (list->set ls)
-    (unless (andmap fixnum? ls) (error 'list->set "~s is not a list of fixnum" ls))
+    (unless (andmap fixnum? ls) (error 'list->set "not a list of fixnum" ls))
     (let f ([ls ls] [s 0])
       (cond
         [(null? ls) s]
@@ -1254,7 +1254,7 @@
       [(disp? x)
        (let-values ([(vs rs fs ns) (R (disp-s0 x) vs rs fs ns)])
           (R (disp-s1 x) vs rs fs ns))]
-      [else (error who "invalid R ~s" x)]))
+      [else (error who "invalid R" x)]))
   (define (R* ls vs rs fs ns)
     (cond
       [(null? ls) (values vs rs fs ns)]
@@ -1299,7 +1299,7 @@
                 (let ([rs (rem-reg d rs)])
                   (mark-reg/vars-conf! d vs)
                   (values vs rs (add-frm s fs) ns))]
-               [else (error who "invalid rs ~s" (unparse x))])]
+               [else (error who "invalid rs" (unparse x))])]
             [(fvar? d) 
              (cond
                [(not (mem-frm? d fs)) 
@@ -1317,7 +1317,7 @@
                   (mark-frm/vars-conf! d vs)
                   (mark-frm/nfvs-conf! d ns)
                   (values (add-var s vs) rs fs ns))]
-               [else (error who "invalid fs ~s" s)])]
+               [else (error who "invalid fs" s)])]
             [(var? d)
              (cond
                [(not (mem-var? d vs)) 
@@ -1356,7 +1356,7 @@
                   (mark-var/regs-conf! d rs)
                   (mark-var/nfvs-conf! d ns)
                   (values vs rs (add-frm s fs) ns))]
-               [else (error who "invalid vs ~s" s)])]
+               [else (error who "invalid vs" s)])]
             [(nfv? d)
              (cond
                [(not (mem-nfv? d ns)) (error who "dead nfv")]
@@ -1377,12 +1377,12 @@
                   (mark-nfv/vars-conf! d vs)
                   (mark-nfv/frms-conf! d fs)
                   (values vs rs (add-frm s fs) ns))]
-               [else (error who "invalid ns ~s" s)])]
-            [else (error who "invalid d ~s" d)])]
+               [else (error who "invalid ns" s)])]
+            [else (error who "invalid d" d)])]
          [(int-/overflow int+/overflow int*/overflow)
           (let ([v (exception-live-set)])
             (unless (vector? v)
-              (error who "unbound exception for ~s ~s" x v))
+              (error who "unbound exception" x v))
             (let ([vs (union-vars vs (vector-ref v 0))]
                   [rs (union-regs rs (vector-ref v 1))]
                   [fs (union-frms fs (vector-ref v 2))]
@@ -1416,7 +1416,7 @@
                       (mark-nfv/vars-conf! d vs)
                       (mark-nfv/frms-conf! d fs)
                       (R s vs rs fs (add-nfv d ns)))])]
-                [else (error who "invalid op d ~s" (unparse x))])))] 
+                [else (error who "invalid op d" (unparse x))])))] 
          [(logand logor logxor sll sra srl int+ int- int*) 
           (cond
             [(var? d) 
@@ -1447,7 +1447,7 @@
                   (mark-nfv/vars-conf! d vs)
                   (mark-nfv/frms-conf! d fs)
                   (R s vs rs fs (add-nfv d ns)))])]
-            [else (error who "invalid op d ~s" (unparse x))])]
+            [else (error who "invalid op d" (unparse x))])]
          [(idiv) 
           (mark-reg/vars-conf! eax vs)
           (mark-reg/vars-conf! edx vs)
@@ -1458,7 +1458,7 @@
          [(mset bset/c bset/h fl:load fl:store fl:add! fl:sub!
                 fl:mul! fl:div! fl:from-int) 
           (R* (list s d) vs rs fs ns)]
-         [else (error who "invalid effect op ~s" (unparse x))])]
+         [else (error who "invalid effect op" (unparse x))])]
       [(ntcall target value args mask size)
        (set! spill-set (union-vars vs spill-set))
        (for-each-var vs varvec (lambda (x) (set-var-loc! x #t)))
@@ -1478,13 +1478,13 @@
                     (vector-ref v 1)
                     (vector-ref v 2)
                     (vector-ref v 3)))]
-         [else (error who "invalid effect op ~s" op)])]
+         [else (error who "invalid effect op" op)])]
       [(shortcut body handler)
        (let-values ([(vsh rsh fsh nsh) (E handler vs rs fs ns)])
           (parameterize ([exception-live-set
                           (vector vsh rsh fsh nsh)])
             (E body vs rs fs ns)))]
-      [else (error who "invalid effect ~s" (unparse x))]))
+      [else (error who "invalid effect" (unparse x))]))
   (define (P x vst rst fst nst 
                vsf rsf fsf nsf
                vsu rsu fsu nsu)
@@ -1527,7 +1527,7 @@
             (P body vst rst fst nst 
                     vsf rsf fsf nsf
                     vsu rsu fsu nsu)))]
-      [else (error who "invalid pred ~s" (unparse x))]))
+      [else (error who "invalid pred" (unparse x))]))
   (define (T x)
     (struct-case x
       [(seq e0 e1) 
@@ -1550,13 +1550,13 @@
               (empty-reg-set) 
               (empty-frm-set)
               (empty-nfv-set))]
-         [else (error who "invalid tail op ~s" x)])]
+         [else (error who "invalid tail op" x)])]
       [(shortcut body handler)
        (let-values ([(vsh rsh fsh nsh) (T handler)])
           (parameterize ([exception-live-set
                           (vector vsh rsh fsh nsh)])
              (T body)))]
-      [else (error who "invalid tail ~s" x)]))
+      [else (error who "invalid tail" x)]))
   (define exception-live-set 
     (make-parameter #f))
   (T x)
@@ -1622,7 +1622,7 @@
                      [else (error who "invalid arg")]))
                  args)
             mask idx)]
-        [else (error who "invalid NF effect ~s" x)]))
+        [else (error who "invalid NF effect" x)]))
     (define (Var x)
       (cond
         [(var-loc x) =>
@@ -1640,7 +1640,7 @@
         [(var? x) (Var x)]
         [(disp? x)
          (make-disp (R (disp-s0 x)) (R (disp-s1 x)))]
-        [else (error who "invalid R ~s" (unparse x))]))
+        [else (error who "invalid R" (unparse x))]))
     (define (E x)
       (struct-case x
         [(seq e0 e1)
@@ -1664,7 +1664,7 @@
               fl:from-int)
             (make-asm-instr op (R d) (R s))]
            [(nop) (make-primcall 'nop '())]
-           [else (error who "invalid op ~s" op)])]
+           [else (error who "invalid op" op)])]
         [(nframe vars live body)
          (let ([live-frms1
                 (map (lambda (i) (Var (vector-ref varvec i)))
@@ -1762,10 +1762,10 @@
         [(primcall op args)
          (case op
            [(nop interrupt incr/zero?) x]
-           [else (error who "invalid effect prim ~s" op)])]
+           [else (error who "invalid effect prim" op)])]
         [(shortcut body handler)
          (make-shortcut (E body) (E handler))]
-        [else (error who "invalid effect ~s" (unparse x))]))
+        [else (error who "invalid effect" (unparse x))]))
     (define (P x)
       (struct-case x
         [(seq e0 e1)
@@ -1777,7 +1777,7 @@
         [(constant) x]
         [(shortcut body handler)
          (make-shortcut (P body) (P handler))]
-        [else (error who "invalid pred ~s" (unparse x))]))
+        [else (error who "invalid pred" (unparse x))]))
     (define (T x)
       (struct-case x
         [(seq e0 e1)
@@ -1788,7 +1788,7 @@
         [(primcall op args) x]
         [(shortcut body handler)
          (make-shortcut (T body) (T handler))]
-        [else (error who "invalid tail ~s" (unparse x))]))
+        [else (error who "invalid tail" (unparse x))]))
     (T x))
   ;;;
   (define (Main x)
@@ -1806,7 +1806,7 @@
                      [(var-loc (car vars)) (f (cdr vars))]
                      [else (cons (car vars) (f (cdr vars)))])))
                body))))]
-      [else (error 'assign-frame-sizes "invalid main ~s" x)]))
+      [else (error 'assign-frame-sizes "invalid main" x)]))
   ;;;
   (define (ClambdaCase x) 
     (struct-case x
@@ -1859,7 +1859,7 @@
             (if (memq x all-registers) 
                 (set-add x (make-empty-set))
                 (make-empty-set))]
-           [else (error who "invalid R ~s" x)])]))
+           [else (error who "invalid R" x)])]))
     ;;; build effect
     (define (E x s)
       (struct-case x
@@ -1910,7 +1910,7 @@
            [(mset fl:load fl:store fl:add! fl:sub! fl:mul! fl:div!
                   fl:from-int)
             (set-union (R v) (set-union (R d) s))]
-           [else (error who "invalid effect ~s" x)])]
+           [else (error who "invalid effect" x)])]
         [(seq e0 e1) (E e0 (E e1 s))]
         [(conditional e0 e1 e2)
          (let ([s1 (E e1 s)] [s2 (E e2 s)])
@@ -1922,12 +1922,12 @@
            [(nop) s]
            [(interrupt incr/zero?) 
             (or (exception-live-set) (error who "uninitialized exception"))]
-           [else (error who "invalid effect primcall ~s" op)])]
+           [else (error who "invalid effect primcall" op)])]
         [(shortcut body handler)
          (let ([s2 (E handler s)])
            (parameterize ([exception-live-set s2])
              (E body s)))]
-        [else (error who "invalid effect ~s" (unparse x))]))
+        [else (error who "invalid effect" (unparse x))]))
     (define (P x st sf su)
       (struct-case x
         [(constant c) (if c st sf)]
@@ -1942,7 +1942,7 @@
          (let ([s2 (P handler st sf su)])
            (parameterize ([exception-live-set s2])
              (P body st sf su)))]
-        [else (error who "invalid pred ~s" (unparse x))]))
+        [else (error who "invalid pred" (unparse x))]))
     (define (T x)
       (struct-case x
         [(conditional e0 e1 e2)
@@ -1955,7 +1955,7 @@
          (let ([s2 (T handler)])
            (parameterize ([exception-live-set s2])
               (T body)))]
-        [else (error who "invalid tail ~s" (unparse x))]))
+        [else (error who "invalid tail" (unparse x))]))
     (define exception-live-set (make-parameter #f))
     (let ([s (T x)])
       ;(pretty-print (unparse x))
@@ -1986,7 +1986,7 @@
               (car r*)))))
     (define (find-color x confs env)
       (or (find-color/maybe x confs env)
-          (error 'find-color "cannot find color for ~s" x)))
+          (error 'find-color "cannot find color for" x)))
     (cond
       [(and (empty-set? sp*) (empty-set? un*)) 
        (values '() (make-empty-set) '())]
@@ -2041,7 +2041,7 @@
       (struct-case x
         [(var) (Var x)]
         [(nfv confs loc) 
-         (or loc (error who "LHS not set ~s" x))]
+         (or loc (error who "LHS not set" x))]
         [else x]))
     (define (D x)
       (struct-case x
@@ -2049,17 +2049,17 @@
         [(var) (Var x)]
         [(fvar) x]
         [else
-         (if (symbol? x) x (error who "invalid D ~s" x))]))
+         (if (symbol? x) x (error who "invalid D" x))]))
     (define (R x)
       (struct-case x
         [(constant) x]
         [(var) (Var x)]
         [(fvar)     x]
         [(nfv c loc)
-         (or loc (error who "unset nfv ~s in R" x))]
+         (or loc (error who "unset nfv in R" x))]
         [(disp s0 s1) (make-disp (D s0) (D s1))]
         [else
-         (if (symbol? x) x (error who "invalid R ~s" x))]))
+         (if (symbol? x) x (error who "invalid R" x))]))
     ;;; substitute effect
     (define (E x)
       (struct-case x
@@ -2073,7 +2073,7 @@
         [(ntcall) x]
         [(shortcut body handler)
          (make-shortcut (E body) (E handler))]
-        [else (error who "invalid effect ~s" (unparse x))]))
+        [else (error who "invalid effect" (unparse x))]))
     (define (P x)
       (struct-case x
         [(constant) x]
@@ -2084,7 +2084,7 @@
         [(seq e0 e1) (make-seq (E e0) (P e1))]
         [(shortcut body handler)
          (make-shortcut (P body) (P handler))]
-        [else (error who "invalid pred ~s" (unparse x))])) 
+        [else (error who "invalid pred" (unparse x))])) 
     (define (T x)
       (struct-case x
         [(primcall op rands) x]
@@ -2093,7 +2093,7 @@
         [(seq e0 e1) (make-seq (E e0) (T e1))]
         [(shortcut body handler)
          (make-shortcut (T body) (T handler))]
-        [else (error who "invalid tail ~s" (unparse x))]))
+        [else (error who "invalid tail" (unparse x))]))
     ;(print-code x)
     (T x))
   ;;;
@@ -2195,12 +2195,12 @@
               (error who "invalid arg to idiv"))
             (cond
               [(disp? b)
-               (error who "invalid arg to idiv ~s" b)]
+               (error who "invalid arg to idiv" b)]
               [else x])]
            [(sll sra srl)
             (unless (or (constant? b)
                         (eq? b ecx))
-              (error who "invalid shift ~s" b))
+              (error who "invalid shift" b))
             x]
            [(mset bset/c bset/h) 
             (cond
@@ -2241,16 +2241,16 @@
                    (E (make-asm-instr op u b))))]
               [else x])]
            [(fl:from-int) x]
-           [else (error who "invalid effect ~s" op)])]
+           [else (error who "invalid effect" op)])]
         [(primcall op rands) 
          (case op
            [(nop interrupt incr/zero?) x]
-           [else (error who "invalid op in ~s" (unparse x))])]
+           [else (error who "invalid op in" (unparse x))])]
         [(ntcall) x]
         [(shortcut body handler)
          (let ([body (E body)])
            (make-shortcut body (E handler)))]
-        [else (error who "invalid effect ~s" (unparse x))]))
+        [else (error who "invalid effect" (unparse x))]))
     (define (P x)
       (struct-case x
         [(constant) x]
@@ -2284,7 +2284,7 @@
         [(shortcut body handler)
          (let ([body (P body)])
            (make-shortcut body (P handler)))]
-        [else (error who "invalid pred ~s" (unparse x))]))
+        [else (error who "invalid pred" (unparse x))]))
     (define (T x)
       (struct-case x
         [(primcall op rands) x]
@@ -2293,7 +2293,7 @@
         [(seq e0 e1) (make-seq (E e0) (T e1))]
         [(shortcut body handler)
          (make-shortcut (T body) (T handler))]
-        [else (error who "invalid tail ~s" (unparse x))]))
+        [else (error who "invalid tail" (unparse x))]))
     (let ([x (T x)])
       (values un* x)))
   ;;;
@@ -2355,19 +2355,19 @@
       [else 
        (if (integer? x)
            x
-           (error who "invalid constant C ~s" x))]))
+           (error who "invalid constant C" x))]))
   (define (BYTE x)
     (struct-case x
       [(constant x)
        (unless (and (integer? x) (fx<= x 255) (fx<= -128 x))
-         (error who "invalid byte ~s" x))
+         (error who "invalid byte" x))
        x]
-      [else (error who "invalid byte ~s" x)]))
+      [else (error who "invalid byte" x)]))
   (define (D x)
     (struct-case x
       [(constant c) (C c)]
       [else
-       (if (symbol? x) x (error who "invalid D ~s" x))]))
+       (if (symbol? x) x (error who "invalid D" x))]))
   (define (R x)
     (struct-case x
       [(constant c) (C c)]
@@ -2376,7 +2376,7 @@
        (let ([s0 (D s0)] [s1 (D s1)])
          `(disp ,s0 ,s1))]
       [else
-       (if (symbol? x) x (error who "invalid R ~s" x))]))
+       (if (symbol? x) x (error who "invalid R" x))]))
   (define (R/l x)
     (struct-case x
       [(constant c) (C c)]
@@ -2385,27 +2385,27 @@
        (let ([s0 (D s0)] [s1 (D s1)])
          `(disp ,s0 ,s1))]
       [else
-       (if (symbol? x) (reg/l x) (error who "invalid R/l ~s" x))])) 
+       (if (symbol? x) (reg/l x) (error who "invalid R/l" x))])) 
   (define (reg/h x)
     (cond
       [(assq x '([%eax %ah] [%ebx %bh] [%ecx %ch] [%edx %dh]))
        => cadr]
-      [else (error who "invalid reg/h ~s" x)]))
+      [else (error who "invalid reg/h" x)]))
   (define (reg/l x)
     (cond
       [(assq x '([%eax %al] [%ebx %bl] [%ecx %cl] [%edx %dl]))
        => cadr]
-      [else (error who "invalid reg/l ~s" x)])) 
+      [else (error who "invalid reg/l" x)])) 
   (define (R/cl x)
     (struct-case x
       [(constant i) 
        (unless (fixnum? i)
-         (error who "invalid R/cl ~s" x))
+         (error who "invalid R/cl" x))
        (fxlogand i 31)]
       [else
        (if (eq? x ecx)
            '%cl
-           (error who "invalid R/cl ~s" x))]))
+           (error who "invalid R/cl" x))]))
   (define (interrupt? x)
     (struct-case x
       [(primcall op args) (eq? op 'interrupt)]
@@ -2532,7 +2532,7 @@
           (cons `(mulsd ,(R (make-disp s d)) xmm0) ac)]
          [(fl:div!) 
           (cons `(divsd ,(R (make-disp s d)) xmm0) ac)]
-         [else (error who "invalid instr ~s" x)])]
+         [else (error who "invalid instr" x)])]
       [(primcall op rands)
        (case op
          [(nop) ac]
@@ -2547,7 +2547,7 @@
               `(addl 1 ,(R (make-disp (car rands) (cadr rands))))
               `(je ,l)
               ac))]
-         [else (error who "invalid effect ~s" (unparse x))])]
+         [else (error who "invalid effect" (unparse x))])]
       [(shortcut body handler)
        (let ([L (unique-interrupt-label)] [L2 (unique-label)])
          (let ([hand (cons L (E handler `((jmp ,L2))))])
@@ -2560,7 +2560,7 @@
       ;   (let ([ac (cons L (E handler (cons L2 ac)))])
       ;     (parameterize ([exception-label L])
       ;        (E body (cons `(jmp ,L2) ac)))))]
-      [else (error who "invalid effect ~s" (unparse x))]))
+      [else (error who "invalid effect" (unparse x))]))
   ;;;
   (define (unique-interrupt-label)
     (label (gensym "ERROR")))
@@ -2609,7 +2609,7 @@
                         [fl:> fl:o<=] [fl:>= fl:o<]
                         ))
               => cadr]
-             [else (error who "invalid notop ~s" x)]))
+             [else (error who "invalid notop" x)]))
          (define (jmpname x)
            (cond
              [(assq x '([= je] [!= jne] [< jl] [<= jle] [> jg] [>= jge]
@@ -2620,13 +2620,13 @@
                         [fl:o< jb] [fl:o> ja] [fl:o<= jbe] [fl:o>= jae]
                         ))
               => cadr]
-             [else (error who "invalid jmpname ~s" x)]))
+             [else (error who "invalid jmpname" x)]))
          (define (revjmpname x)
            (cond
              [(assq x '([= je] [!= jne] [< jg] [<= jge] [> jl] [>= jle]
                         [u< ja] [u<= jae] [u> jb] [u>= jbe]))
               => cadr]
-             [else (error who "invalid jmpname ~s" x)]))
+             [else (error who "invalid jmpname" x)]))
          (define (cmp op a0 a1 lab ac)
            (cond
              [(memq op '(fl:= fl:!= fl:< fl:<= fl:> fl:>=))
@@ -2647,7 +2647,7 @@
               (cons* `(cmpl ,(R a0) ,(R a1))
                      `(,(revjmpname op) ,lab)
                      ac)]
-             [else (error who "invalid cmpops ~s ~s" a0 a1)]))
+             [else (error who "invalid cmpops" a0 a1)]))
          (cond
            [(and lt lf)
             (cmp op a0 a1 lt
@@ -2665,7 +2665,7 @@
                (set-cdr! tc (append hand (cdr tc)))))
            (parameterize ([exception-label L])
              (P body lt lf ac))))]
-      [else (error who "invalid pred ~s" x)]))
+      [else (error who "invalid pred" x)]))
   ;;;
   (define (T x ac)
     (struct-case x
@@ -2681,7 +2681,7 @@
                ac)]
         [(direct-jump)
          (cons `(jmp (label ,(code-loc-label (car rands)))) ac)]
-        [else (error who "invalid tail ~s" x)])]
+        [else (error who "invalid tail" x)])]
       [(shortcut body handler) 
        (let ([L (unique-interrupt-label)])
          (let ([hand (cons L (T handler '()))])
@@ -2689,7 +2689,7 @@
              (set-cdr! tc (append hand (cdr tc)))))
          (parameterize ([exception-label L])
            (T body ac)))]
-      [else (error who "invalid tail ~s" x)]))
+      [else (error who "invalid tail" x)]))
   (define exception-label (make-parameter #f))
   ;;;
   (define (handle-vararg fml-count ac)
diff --git a/scheme/ikarus.compiler.ss b/scheme/ikarus.compiler.ss
index 2b70da3..88eb31d 100644
--- a/scheme/ikarus.compiler.ss
+++ b/scheme/ikarus.compiler.ss
@@ -27,7 +27,7 @@
            #'(i . i*))]))
     (define (generate-body ctxt cls*)
       (syntax-case cls* (else)
-        [() (with-syntax ([x x]) #'(error #f "unmatched ~s in ~s" v 'x))]
+        [() (with-syntax ([x x]) #'(error #f "unmatched " v 'x))]
         [([else b b* ...])  #'(begin b b* ...)]
         [([(rec-name rec-field* ...) b b* ...] . rest) (identifier? #'rec-name)
          (with-syntax ([altern (generate-body ctxt #'rest)]
@@ -144,7 +144,7 @@
             (let ([fv (make-fvar i)])
               (set! cache (cons (cons i fv) cache))
               fv)])]
-        [else (error 'mkfvar "~s is not a fixnum" i)]))))
+        [else (error 'mkfvar "not a fixnum" i)]))))
 
 (define (unique-var x)
   (make-var (gensym x) #f #f #f #f #f #f #f #f #f #f))
@@ -181,17 +181,17 @@
              (eq? 'quote (car x))
              (symbol? (cadr x)))
         (cadr x)
-        (error 'quoted-sym "not a quoted symbol ~s" x)))
+        (error 'quoted-sym "not a quoted symbol" x)))
   (define (quoted-string x)
     (if (and (list? x)
              (fx= (length x) 2)
              (eq? 'quote (car x))
              (string? (cadr x)))
         (cadr x)
-        (error 'quoted-string "not a quoted string ~s" x)))
+        (error 'quoted-string "not a quoted string" x)))
   (define (Var x)
     (or (getprop x *cookie*) 
-        (error 'recordize "unbound ~s" x)))
+        (error 'recordize "unbound" x)))
   (define (lexical x) 
     (getprop x *cookie*))
   (define (get-fmls x args) 
@@ -292,7 +292,7 @@
            (make-funcall 
              (make-primref 'top-level-value) 
              (list (make-constant x))))]
-      [else (error 'recordize "invalid expression ~s" x)]))
+      [else (error 'recordize "invalid expression" x)]))
   (E x #f))
 
 (define (unparse x)
@@ -454,8 +454,6 @@
         [(conditional) #f]
         [(bind lhs* rhs* body) (valid-mv-producer? body)]
         [else #f] ;; FIXME BUG
-       ; [else (error 'valid-mv-producer? "unhandles ~s"
-       ;              (unparse x))]
         ))
     (struct-case rator
       [(clambda g cls*)
@@ -514,7 +512,7 @@
        (make-forcall rator (map Expr rand*))]
       [(assign lhs rhs)
        (make-assign lhs (Expr rhs))]
-      [else (error who "invalid expression ~s" (unparse x))]))
+      [else (error who "invalid expression" (unparse x))]))
   (Expr x))
 
 
@@ -673,8 +671,8 @@
          (make-mvcall p c))]
       [(forcall rator rand*) 
        (make-forcall rator (E* rand* ref comp))]
-      [else (error who "invalid expression ~s" (unparse x))]))
-  (E x (lambda (x) (error who "free var ~s found" x))
+      [else (error who "invalid expression" (unparse x))]))
+  (E x (lambda (x) (error who "free var found" x))
        void))
 
 
@@ -718,7 +716,7 @@
       [(assign lhs rhs)
        (set-var-assigned! lhs #t)
        (Expr rhs)]
-      [else (error who "invalid expression ~s" (unparse x))]))
+      [else (error who "invalid expression" (unparse x))]))
   (Expr x)
   x)
 
@@ -937,7 +935,8 @@
                              (make-funcall (make-primref op)
                                 (list a0 (make-constant n1))))))
                        (make-funcall (make-primref op) rand*))])))
-         (error 'optimize "~s rands to ~s" (map unparse rand*) op))]
+         (error 'optimize "invalid operands to primitive"
+            (map unparse rand*) op))]
     [(void)
      (or (and (null? rand*)
               (case ctxt
@@ -1009,7 +1008,7 @@
                                    "incorrect arg ~s to ~s"
                                    v op))))
                     (giveup))))
-         (error 'optimize "incorrect args ~s to ~s"
+         (error 'optimize "incorrect args to primitive"
                 (map unparse rand*) op))]
     [(fxadd1 fxsub1)
      (or (and (fx= (length rand*) 1)
@@ -1088,7 +1087,7 @@
      (make-seq e0 (mk-mvcall e1 c))]
     [(bind lhs* rhs* body)
      (make-bind lhs* rhs* (mk-mvcall body c))]
-    [else (error 'mk-mvcall "invalid producer ~s" (unparse p))]))
+    [else (error 'mk-mvcall "invalid producer" (unparse p))]))
 
 
 (define (copy-propagate x)
@@ -1230,11 +1229,11 @@
        (mk-mvcall (Value p) (Value c))]
       [(assign lhs rhs)
        (unless (var-assigned lhs)
-         (error who "var ~s is not assigned" lhs))
+         (error who "var is not assigned" lhs))
        (if (var-referenced lhs)
            (make-assign lhs (Value rhs))
            (Effect rhs))]
-      [else (error who "invalid effect expression ~s" (unparse x))]))
+      [else (error who "invalid effect expression" (unparse x))]))
   (define (Pred x)
     (struct-case x
       [(constant) x]
@@ -1288,7 +1287,7 @@
        (mk-seq (Effect x) (make-constant #t))]
       [(mvcall p c)
        (mk-mvcall (Value p) (Value c))]
-      [else (error who "invalid pred expression ~s" (unparse x))]))
+      [else (error who "invalid pred expression" (unparse x))]))
   (define (Value x)
     (struct-case x
       [(constant) x]
@@ -1296,7 +1295,7 @@
        (let ([r (var-referenced x)])
          (case r
            [(#t) x]
-           [(#f) (error who "Reference to a var ~s that should not be" x)]
+           [(#f) (error who "Reference to a var that should not be" x)]
            [else r]))]
       [(primref) x]
       [(bind lhs* rhs* body)
@@ -1340,7 +1339,7 @@
        (mk-seq (Effect x) the-void)]
       [(mvcall p c)
        (mk-mvcall (Value p) (Value c))]
-      [else (error who "invalid value expression ~s" (unparse x))]))
+      [else (error who "invalid value expression" (unparse x))]))
   (let ([x (Value x)])
     ;;; since we messed up the references and assignments here, we
     ;;; redo them
@@ -1405,11 +1404,11 @@
        (make-funcall (Expr rator) (map Expr rand*))]
       [(assign lhs rhs)
        (unless (var-assigned lhs)
-         (error 'rewrite-assignments "not assigned ~s in ~s" lhs x))
+         (error 'rewrite-assignments "not assigned" lhs x))
        (make-funcall (make-primref '$vector-set!)
          (list lhs (make-constant 0) (Expr rhs)))]
       [(mvcall p c) (make-mvcall (Expr p) (Expr c))]
-      [else (error who "invalid expression ~s" (unparse x))]))
+      [else (error who "invalid expression" (unparse x))]))
   (Expr x))
 
 
@@ -1499,7 +1498,7 @@
            [else
             (make-funcall rator (map Expr rand*))]))]
       [(mvcall p c) (make-mvcall (Expr p) (Expr c))]
-      [else (error who "invalid expression ~s" (unparse x))]))
+      [else (error who "invalid expression" (unparse x))]))
   (Expr x))
 
 
@@ -1586,12 +1585,12 @@
            [(closure code free^) 
             (values (make-mvcall p code)
                     (union p-free c-free))]
-           [else (error who "invalid mvcall consumer ~s" 
+           [else (error who "invalid mvcall consumer" 
                         (unparse c))]))]
-      [else (error who "invalid expression ~s" (unparse ex))]))
+      [else (error who "invalid expression" (unparse ex))]))
   (let-values ([(prog free) (Expr prog)])
     (unless (null? free) 
-      (error 'convert-closures "free vars ~s encountered in ~a"
+      (error 'convert-closures "free vars encountered in program"
           free (unparse prog)))
    prog))
 
@@ -1741,7 +1740,7 @@
                         (make-clambda-case info (E body))]))
                    cases)
               free name))])]
-      [else (error who "invalid expression ~s" (unparse x))]))
+      [else (error who "invalid expression" (unparse x))]))
   (let ([x (E x)])
     (make-codes all-codes x)))
 
@@ -1944,7 +1943,7 @@
     (cond
       [(fixnum? off) (list 'disp (int off) val)]
       [(register? off) (list 'disp off val)]
-      [else (error 'mem "invalid disp ~s" off)]))
+      [else (error 'mem "invalid disp" off)]))
   (define-syntax int
     (syntax-rules ()
       [(_ x) x]))
@@ -2027,20 +2026,20 @@
       [(engine-counter)     (mem 36 pcr)]
       [(interrupted)        (mem 40 pcr)]
       [(base-rtd)           (mem 44 pcr)]
-      [else (error 'pcb-ref "invalid arg ~s" x)])))
+      [else (error 'pcb-ref "invalid arg" x)])))
 
 
 (define (primref->symbol op)
-  (unless (symbol? op) (error 'primref->symbol "not a symbol ~s" op))
+  (unless (symbol? op) (error 'primref->symbol "not a symbol" op))
   (cond
     [((current-primitive-locations) op) =>
      (lambda (x)
        (unless (symbol? x) 
          (error 'primitive-location 
-            "~s is not a valid location for ~s" x op))
+            "not a valid location for ~s" x op))
        x)]
     [else
-     (error #f "~s is not supported yet" op)]))
+     (error #f "not supported yet" op)]))
 
 (define (primref-loc op)
   (mem (fx- disp-symbol-record-proc record-tag) 
@@ -2395,7 +2394,7 @@
                  (if (closure? x)
                      (if (null? (closure-free* x))
                          (code-loc-label (closure-code x))
-                         (error 'compile "BUG: non-thunk escaped: ~s" x))
+                         (error 'compile "BUG: non-thunk escaped" x))
                      #f))
                ls*)])
         (car code*)))))
@@ -2426,7 +2425,7 @@
            (begin 
              (set! plocs p) 
              (refresh-cached-labels!))
-           (error 'current-primitive-locations "~s is not a procedure" p))])))
+           (error 'current-primitive-locations "not a procedure" p))])))
 
 )
 
diff --git a/scheme/ikarus.conditions.ss b/scheme/ikarus.conditions.ss
index 194577b..1b55aab 100644
--- a/scheme/ikarus.conditions.ss
+++ b/scheme/ikarus.conditions.ss
@@ -132,7 +132,7 @@
       [(x) 
        (if (condition? x)
            x 
-           (error 'condition "~s is not a condition type" x))]
+           (error 'condition "not a condition type" x))]
       [x*
        (let ([ls
               (let f ([x* x*])
@@ -142,7 +142,7 @@
                    (cons (car x*) (f (cdr x*)))]
                   [(compound-condition? (car x*)) 
                    (append (simple-conditions (car x*)) (f (cdr x*)))]
-                  [else (error 'condition "~s is not a condition" (car x*))]))])
+                  [else (error 'condition "not a condition" (car x*))]))])
          (cond
            [(null? ls) (make-compound-condition '())]
            [(null? (cdr ls)) (car ls)]
@@ -152,13 +152,13 @@
     (cond
       [(compound-condition? x) (compound-condition-components x)]
       [(&condition? x) (list x)]
-      [else (error 'simple-conditions "~s is not a condition" x)]))
+      [else (error 'simple-conditions "not a condition" x)]))
 
   (define (condition-predicate rtd) 
     (unless (rtd? rtd) 
-      (error 'condition-predicate "~s is not a record type descriptor" rtd))
+      (error 'condition-predicate "not a record type descriptor" rtd))
     (unless (rtd-subtype? rtd (record-type-descriptor &condition))
-      (error 'condition-predicate "~s is not a descendant of &condition" rtd))
+      (error 'condition-predicate "not a descendant of &condition" rtd))
     (let ([p? (record-predicate rtd)])
       (lambda (x) 
         (or (p? x) 
@@ -170,11 +170,11 @@
   
   (define (condition-accessor rtd proc) 
     (unless (rtd? rtd) 
-      (error 'condition-accessor "~s is not a record type descriptor" rtd))
+      (error 'condition-accessor "not a record type descriptor" rtd))
     (unless (procedure? proc) 
-      (error 'condition-accessor "~s is not a procedure" proc))
+      (error 'condition-accessor "not a procedure" proc))
     (unless (rtd-subtype? rtd (record-type-descriptor &condition))
-      (error 'condition-accessor "~s is not a descendant of &condition" rtd))
+      (error 'condition-accessor "not a descendant of &condition" rtd))
     (let ([p? (record-predicate rtd)])
       (lambda (x) 
         (cond
@@ -187,9 +187,9 @@
                     (proc (car ls))
                     (f (cdr ls)))]
                [else
-                (error 'condition-accessor "~s is not a condition of type ~s" x rtd)]))]
+                (error 'condition-accessor "not a condition of correct type" x rtd)]))]
           [else 
-           (error 'condition-accessor "~s is not a condition of type ~s" x rtd)]))))
+           (error 'condition-accessor "not a condition of correct type" x rtd)]))))
 
   (define-syntax define-condition-type
     (lambda (x)
@@ -358,7 +358,7 @@
         [(x port)
          (if (output-port? port) 
              (print-condition x port)
-             (error 'print-condition "~s is not an output port" port))])))
+             (error 'print-condition "not an output port" port))])))
 
   )
 
diff --git a/scheme/ikarus.control.ss b/scheme/ikarus.control.ss
index 61b0b43..0e5bd1a 100644
--- a/scheme/ikarus.control.ss
+++ b/scheme/ikarus.control.ss
@@ -17,7 +17,7 @@
     (lambda (f)
       (if (procedure? f)
           (primitive-call/cf f)
-          (error 'call/cf "~s is not a procedure" f))))
+          (error 'call/cf "not a procedure" f))))
 
   (define primitive-call/cc
     (lambda (f)
@@ -77,7 +77,7 @@
   (define call/cc
     (lambda (f)
       (unless (procedure? f) 
-        (error 'call/cc "~s is not a procedure" f))
+        (error 'call/cc "not a procedure" f))
       (primitive-call/cc
         (lambda (k)
           (let ([save winders])
@@ -92,17 +92,17 @@
     (lambda (f)
       (unless (procedure? f) 
         (error 'call-with-current-continuation
-            "~s is not a procedure" f))
+            "not a procedure" f))
       (call/cc f)))
 
   (define dynamic-wind
     (lambda (in body out)
       (unless (procedure? in)
-        (error 'dynamic-wind "~s is not a procedure" in))
+        (error 'dynamic-wind "not a procedure" in))
       (unless (procedure? body)
-        (error 'dynamic-wind "~s is not a procedure" body))
+        (error 'dynamic-wind "not a procedure" body))
       (unless (procedure? out)
-        (error 'dynamic-wind "~s is not a procedure" out))
+        (error 'dynamic-wind "not a procedure" out))
       (in)
       (set! winders (cons (cons in out) winders))
       (call-with-values
diff --git a/scheme/ikarus.exceptions.ss b/scheme/ikarus.exceptions.ss
index b75a352..3f16613 100644
--- a/scheme/ikarus.exceptions.ss
+++ b/scheme/ikarus.exceptions.ss
@@ -20,10 +20,9 @@
   (define (with-exception-handler handler proc2)
     (unless (procedure? handler)
       (error 'with-exception-handler
-        "handler ~s is not a procedure" handler))
+        "handler is not a procedure" handler))
     (unless (procedure? proc2)
-      (error 'with-exception-handler
-        "~s is not a procedure" proc2))
+      (error 'with-exception-handler "not a procedure" proc2))
     (parameterize ([handlers (cons handler (handlers))])
       (proc2)))
   
@@ -45,7 +44,7 @@
 
   (define (error who msg . irritants) 
     (unless (string? msg) 
-      (error 'error "message ~s is not a string" msg))
+      (error 'error "message is not a string" msg))
     (raise
        (condition
          (make-error)
diff --git a/scheme/ikarus.fasl.ss b/scheme/ikarus.fasl.ss
index 3492b9f..76b099d 100644
--- a/scheme/ikarus.fasl.ss
+++ b/scheme/ikarus.fasl.ss
@@ -48,7 +48,8 @@
   (define who 'fasl-read)
   (define (assert-eq? x y)
     (unless (eq? x y)
-      (error who "Expected ~s, got ~s\n" y x)))
+      (error who 
+        (format "Expected ~s, got ~s\n" y x))))
   (define (char->int x)
     (if (char? x)
         (char->integer x)
@@ -99,7 +100,7 @@
       (cond
         [(fx< m (vector-length marks))
          (when (vector-ref marks m)
-           (error 'fasl-read "mark ~s set twice" m))
+           (error 'fasl-read "mark set twice" m))
          (vector-set! marks m obj)]
         [else
          (let ([n (vector-length marks)])
@@ -142,7 +143,7 @@
           [(#\<) 
            (let ([cm (read-int p)])
              (unless (fx< cm (vector-length marks))
-               (error who "invalid mark ~s\n" m))
+               (error who "invalid mark" m))
              (let ([code (vector-ref marks cm)])
                (let ([proc ($code->closure code)])
                  (when m (put-mark m proc))
@@ -152,7 +153,7 @@
              (assert-eq? (read-char p) #\x)
              (let ([code (read-code cm m)])
                (if m (vector-ref marks m) ($code->closure code))))]
-          [else (error who "invalid code header ~s" c)])))
+          [else (error who "invalid code header" c)])))
     (define (read/mark m)
       (define (nom)
         (when m (error who "unhandled mark")))
@@ -244,10 +245,10 @@
           [(#\<)
            (let ([m (read-int p)])
              (unless (fx< m (vector-length marks))
-               (error who "invalid mark ~s\n" m))
+               (error who "invalid mark" m))
              (vector-ref marks m))]
           [else
-           (error who "Unexpected ~s as a fasl object header" h)])))
+           (error who "Unexpected char as a fasl object header" h)])))
     (read))
   (define $fasl-read
     (lambda (p)
@@ -263,7 +264,7 @@
       [(p) 
        (if (input-port? p) 
            ($fasl-read p)
-           (error 'fasl-read "~s is not an input port" p))]))
+           (error 'fasl-read "not an input port" p))]))
 
   )
 
diff --git a/scheme/ikarus.fasl.write.ss b/scheme/ikarus.fasl.write.ss
index b62aa76..f1980e8 100644
--- a/scheme/ikarus.fasl.write.ss
+++ b/scheme/ikarus.fasl.write.ss
@@ -18,14 +18,14 @@
 
   (define write-fixnum 
     (lambda (x p)
-      (unless (fixnum? x) (error 'write-fixnum "not a fixnum ~s" x))
+      (unless (fixnum? x) (error 'write-fixnum "not a fixnum" x))
       (write-byte (fxsll (fxlogand x #x3F) 2) p)
       (write-byte (fxlogand (fxsra x 6) #xFF) p)
       (write-byte (fxlogand (fxsra x 14) #xFF) p)
       (write-byte (fxlogand (fxsra x 22) #xFF) p)))
   (define write-int 
     (lambda (x p)
-      (unless (fixnum? x) (error 'write-int "not a fixnum ~s" x))
+      (unless (fixnum? x) (error 'write-int "not a fixnum" x))
       (write-byte (fxlogand x #xFF) p)
       (write-byte (fxlogand (fxsra x 8) #xFF) p)
       (write-byte (fxlogand (fxsra x 16) #xFF) p)
@@ -52,7 +52,7 @@
          (write-char (if x #\T #\F) p)]
         [(eof-object? x) (write-char #\E p)]
         [(eq? x (void)) (write-char #\U p)]
-        [else (error 'fasl-write "~s is not a fasl-writable immediate" x)])))
+        [else (error 'fasl-write "not a fasl-writable immediate" x)])))
   
   (define (ascii-string? s)
     (let f ([s s] [i 0] [n (string-length s)])
@@ -202,7 +202,7 @@
                (write-byte ($bignum-byte-ref x i) p)
                (f (fxadd1 i)))))
          m]
-        [else (error 'fasl-write "~s is not fasl-writable" x)])))
+        [else (error 'fasl-write "not fasl-writable" x)])))
   (define (write-bytevector x i j p)
     (unless ($fx= i j)
       ($write-byte ($bytevector-u8-ref x i) p)
@@ -214,7 +214,7 @@
         [(hashtable-ref h x #f) =>
          (lambda (mark)
            (unless (fixnum? mark)
-             (error 'fasl-write "BUG: invalid mark ~s" mark))
+             (error 'fasl-write "BUG: invalid mark" mark))
            (cond
              [(fx= mark 0) ; singly referenced
               (do-write x p h m)]
@@ -227,7 +227,7 @@
               (write-char #\< p)
               (write-int (fx- 0 mark) p)
               m]))]
-        [else (error 'fasl-write "BUG: not in hash table ~s" x)]))) 
+        [else (error 'fasl-write "BUG: not in hash table" x)]))) 
   (define make-graph
     (lambda (x h)
       (unless (immediate? x)
@@ -275,7 +275,7 @@
               (let ([code ($closure-code x)])
                 (unless (fxzero? (code-freevars code))
                   (error 'fasl-write
-                         "Cannot write a non-thunk procedure; the one given has ~s free vars"
+                         "Cannot write a non-thunk procedure; the one given has free vars"
                          (code-freevars code)))
                 (make-graph code h))]
              [(bytevector? x) (void)]
@@ -284,7 +284,7 @@
              [(ratnum? x) 
               (make-graph (numerator x) h)
               (make-graph (denominator x) h)]
-             [else (error 'fasl-write "~s is not fasl-writable" x)])]))))
+             [else (error 'fasl-write "not fasl-writable" x)])]))))
   (define fasl-write-to-port
     (lambda (x port)
       (let ([h (make-eq-hashtable)])
@@ -302,5 +302,5 @@
        [(x) (fasl-write-to-port x (current-output-port))]
        [(x port)
         (unless (output-port? port)
-          (error 'fasl-write "~s is not an output port" port))
+          (error 'fasl-write "not an output port" port))
         (fasl-write-to-port x port)])))
diff --git a/scheme/ikarus.fixnums.ss b/scheme/ikarus.fixnums.ss
index 7d76d33..a794681 100644
--- a/scheme/ikarus.fixnums.ss
+++ b/scheme/ikarus.fixnums.ss
@@ -35,39 +35,39 @@
       (cond
         [(eq? x 0) #t]
         [(fixnum? x) #f]
-        [else (error 'fxzero? "~s is not a fixnum" x)])))
+        [else (error 'fxzero? "not a fixnum" x)])))
   
   (define fxadd1
     (lambda (n)
       (if (fixnum? n)
           ($fxadd1 n)
-          (error 'fxadd1 "~s is not a fixnum" n))))
+          (error 'fxadd1 "not a fixnum" n))))
   
   (define fxsub1 
     (lambda (n) 
       (if (fixnum? n)
           ($fxsub1 n)
-          (error 'fxsub1 "~s is not a fixnum" n))))
+          (error 'fxsub1 "not a fixnum" n))))
 
   (define fxlognot 
     (lambda (x)
       (unless (fixnum? x) 
-        (error 'fxlognot "~s is not a fixnum" x))
+        (error 'fxlognot "not a fixnum" x))
       ($fxlognot x)))
 
   (define fxnot 
     (lambda (x)
       (unless (fixnum? x) 
-        (error 'fxnot "~s is not a fixnum" x))
+        (error 'fxnot "not a fixnum" x))
       ($fxlognot x)))
   
   (define error@fx+
     (lambda (x y) 
       (if (fixnum? x) 
           (if (fixnum? y) 
-              (error 'fx+ "overflow when adding ~s and ~s" x y)
-              (error 'fx+ "~s is not a fixnum" y))
-          (error 'fx+ "~s is not a fixnum" x))))
+              (error 'fx+ "overflow when adding numbers" x y)
+              (error 'fx+ "not a fixnum" y))
+          (error 'fx+ "not a fixnum" x))))
 
   (define fx+ 
     (lambda (x y) 
@@ -76,17 +76,17 @@
   (define fx-
     (lambda (x y) 
       (unless (fixnum? x)
-        (error 'fx- "~s is not a fixnum" x))
+        (error 'fx- "not a fixnum" x))
       (unless (fixnum? y)
-        (error 'fx- "~s is not a fixnum" y))
+        (error 'fx- "not a fixnum" y))
       ($fx- x y)))
 
   (define fx*
     (lambda (x y) 
       (unless (fixnum? x)
-        (error 'fx* "~s is not a fixnum" x))
+        (error 'fx* "not a fixnum" x))
       (unless (fixnum? y)
-        (error 'fx* "~s is not a fixnum" y))
+        (error 'fx* "not a fixnum" y))
       ($fx* x y)))
   
 
@@ -95,7 +95,7 @@
       (if (pair? ls) 
           (if (fixnum? ($car ls)) 
               (false-loop who ($cdr ls))
-              (error who "~s is not a fixnum" ($car ls)))
+              (error who "not a fixnum" ($car ls)))
           #f)))
 
   (define-syntax fxcmp 
@@ -104,9 +104,9 @@
        (case-lambda
          [(x y) 
           (unless (fixnum? x)
-            (error 'who "~s is not a fixnum" x))
+            (error 'who "not a fixnum" x))
           (unless (fixnum? y)
-            (error 'who "~s is not a fixnum" y))
+            (error 'who "not a fixnum" y))
           ($op x y)]
          [(x y . ls)
           (if (fixnum? x)
@@ -119,13 +119,13 @@
                                   (if ($op x y) 
                                       (f y ls)
                                       (false-loop 'who ls))
-                                  (error 'who "~s is not a fixnum" y)))
+                                  (error 'who "not a fixnum" y)))
                             #t))
                       (false-loop 'who ls))
-                  (error 'who "~s is not a fixnum" y))
-              (error 'who "~s is not a fixnum" x))]
+                  (error 'who "not a fixnum" y))
+              (error 'who "not a fixnum" x))]
          [(x) 
-          (if (fixnum? x) #t (error 'who "~s is not a fixnum" x))])]))
+          (if (fixnum? x) #t (error 'who "not a fixnum" x))])]))
   
   (define fx=   (fxcmp fx= $fx=))
   (define fx<   (fxcmp fx< $fx<))
@@ -142,32 +142,32 @@
   (define fxquotient
     (lambda (x y) 
       (unless (fixnum? x)
-        (error 'fxquotient "~s is not a fixnum" x))
+        (error 'fxquotient "not a fixnum" x))
       (unless (fixnum? y)
-        (error 'fxquotient "~s is not a fixnum" y))
+        (error 'fxquotient "not a fixnum" y))
       (when ($fxzero? y)
-        (error 'fxquotient "zero dividend ~s" y))
+        (error 'fxquotient "zero dividend" y))
       ($fxquotient x y))) 
   
   (define fxremainder
     (lambda (x y) 
       (unless (fixnum? x)
-        (error 'fxremainder "~s is not a fixnum" x))
+        (error 'fxremainder "not a fixnum" x))
       (unless (fixnum? y)
-        (error 'fxremainder "~s is not a fixnum" y))
+        (error 'fxremainder "not a fixnum" y))
       (when ($fxzero? y)
-        (error 'fxremainder "zero dividend ~s" y))
+        (error 'fxremainder "zero dividend" y))
       (let ([q ($fxquotient x y)])
         ($fx- x ($fx* q y)))))
    
   (define fxmodulo
     (lambda (x y) 
       (unless (fixnum? x)
-        (error 'fxmodulo "~s is not a fixnum" x))
+        (error 'fxmodulo "not a fixnum" x))
       (unless (fixnum? y)
-        (error 'fxmodulo "~s is not a fixnum" y))
+        (error 'fxmodulo "not a fixnum" y))
       (when ($fxzero? y)
-        (error 'fxmodulo "zero dividend ~s" y))
+        (error 'fxmodulo "zero dividend" y))
       ($fxmodulo x y)))
 
   (define-syntax fxbitop
@@ -178,8 +178,8 @@
           (if (fixnum? x) 
               (if (fixnum? y) 
                   ($op x y)
-                  (error 'who "~s is not a fixnum" y))
-              (error 'who "~s is not a fixnum" x))]
+                  (error 'who "not a fixnum" y))
+              (error 'who "not a fixnum" x))]
          [(x y . ls) 
           (if (fixnum? x)
               (if (fixnum? y) 
@@ -189,11 +189,11 @@
                        (let ([b ($car ls)])
                          (if (fixnum? b) 
                              (f ($op a b) ($cdr ls))
-                             (error 'who "~s is not a fixnum" b)))]
+                             (error 'who "not a fixnum" b)))]
                       [else a]))
-                  (error 'who "~s is not a fixnum" y))
-              (error 'who "~s is not a fixnum" x))]
-         [(x) (if (fixnum? x) x (error 'who "~s is not a fixnum" x))]
+                  (error 'who "not a fixnum" y))
+              (error 'who "not a fixnum" x))]
+         [(x) (if (fixnum? x) x (error 'who "not a fixnum" x))]
          [()   identity])]))
 
   (define fxlogor (fxbitop fxlogor $fxlogor 0))
@@ -210,58 +210,58 @@
                 ($fxlogor 
                   ($fxlogand x y) 
                   ($fxlogand ($fxlognot x) z))
-                (error 'fxif "~s is not a fixnum" z))
-            (error 'fxif "~s is not a fixnum" y))
-        (error 'fxif "~s is not a fixnum" x)))
+                (error 'fxif "not a fixnum" z))
+            (error 'fxif "not a fixnum" y))
+        (error 'fxif "not a fixnum" x)))
 
   (define fxsra
     (lambda (x y) 
       (unless (fixnum? x)
-        (error 'fxsra "~s is not a fixnum" x))
+        (error 'fxsra "not a fixnum" x))
       (unless (fixnum? y)
-        (error 'fxsra "~s is not a fixnum" y))
+        (error 'fxsra "not a fixnum" y))
       (unless ($fx>= y 0)
-        (error 'fxsra "negative shift not allowed, got ~s" y))
+        (error 'fxsra "negative shift not allowed" y))
       ($fxsra x y)))
    
 
   (define fxarithmetic-shift-right
     (lambda (x y) 
       (unless (fixnum? x)
-        (error 'fxarithmetic-shift-right "~s is not a fixnum" x))
+        (error 'fxarithmetic-shift-right "not a fixnum" x))
       (unless (fixnum? y)
-        (error 'fxarithmetic-shift-right "~s is not a fixnum" y))
+        (error 'fxarithmetic-shift-right "not a fixnum" y))
       (unless ($fx>= y 0)
-        (error 'fxarithmetic-shift-right "negative shift not allowed, got ~s" y))
+        (error 'fxarithmetic-shift-right "negative shift not allowed" y))
       ($fxsra x y)))
 
   (define fxsll
     (lambda (x y) 
       (unless (fixnum? x)
-        (error 'fxsll "~s is not a fixnum" x))
+        (error 'fxsll "not a fixnum" x))
       (unless (fixnum? y)
-        (error 'fxsll "~s is not a fixnum" y))
+        (error 'fxsll "not a fixnum" y))
       (unless ($fx>= y 0)
-        (error 'fxsll "negative shift not allowed, got ~s" y))
+        (error 'fxsll "negative shift not allowed" y))
       ($fxsll x y))) 
 
 
   (define fxarithmetic-shift-left
     (lambda (x y) 
       (unless (fixnum? x)
-        (error 'fxarithmetic-shift-left "~s is not a fixnum" x))
+        (error 'fxarithmetic-shift-left "not a fixnum" x))
       (unless (fixnum? y)
-        (error 'fxarithmetic-shift-left "~s is not a fixnum" y))
+        (error 'fxarithmetic-shift-left "not a fixnum" y))
       (unless ($fx>= y 0)
-        (error 'fxarithmetic-shift-left "negative shift not allowed, got ~s" y))
+        (error 'fxarithmetic-shift-left "negative shift not allowed" y))
       ($fxsll x y)))
 
   (define fxarithmetic-shift
     (lambda (x y) 
       (unless (fixnum? x)
-        (error 'fxarithmetic-shift "~s is not a fixnum" x))
+        (error 'fxarithmetic-shift "not a fixnum" x))
       (unless (fixnum? y)
-        (error 'fxarithmetic-shift "~s is not a fixnum" y))
+        (error 'fxarithmetic-shift "not a fixnum" y))
       (if ($fx>= y 0)
           ($fxsll x y)
           (if ($fx< x -100) ;;; arbitrary number < (fixnum-width)
@@ -271,22 +271,22 @@
   (define (fxpositive? x)
     (if (fixnum? x) 
         ($fx> x 0)
-        (error 'fxpositive? "~s is not a fixnum" x)))
+        (error 'fxpositive? "not a fixnum" x)))
 
   (define (fxnegative? x)
     (if (fixnum? x) 
         ($fx< x 0)
-        (error 'fxnegative? "~s is not a fixnum" x)))
+        (error 'fxnegative? "not a fixnum" x)))
   
   (define (fxeven? x)
     (if (fixnum? x) 
         ($fxzero? ($fxlogand x 1))
-        (error 'fxeven? "~s is not a fixnum" x)))
+        (error 'fxeven? "not a fixnum" x)))
 
   (define (fxodd? x)
     (if (fixnum? x) 
         (not ($fxzero? ($fxlogand x 1)))
-        (error 'fxodd? "~s is not a fixnum" x)))
+        (error 'fxodd? "not a fixnum" x)))
 
   (define fxmin
     (case-lambda 
@@ -294,8 +294,8 @@
        (if (fixnum? x) 
            (if (fixnum? y) 
                (if ($fx< x y) x y)
-               (error 'fxmin "~s is not a fixnum" y))
-           (error 'fxmin "~s is not a fixnum" x))]
+               (error 'fxmin "not a fixnum" y))
+           (error 'fxmin "not a fixnum" x))]
       [(x y z . ls)
        (fxmin (fxmin x y) 
          (if (fixnum? z) 
@@ -307,9 +307,9 @@
                          (if ($fx< a z) 
                              (f a ($cdr ls))
                              (f z ($cdr ls)))
-                         (error 'fxmin "~s is not a fixnum" a)))))
-             (error 'fxmin "~s is not a fixnum" z)))]
-      [(x) (if (fixnum? x) x (error 'fxmin "~s is not a fixnum" x))]))
+                         (error 'fxmin "not a fixnum" a)))))
+             (error 'fxmin "not a fixnum" z)))]
+      [(x) (if (fixnum? x) x (error 'fxmin "not a fixnum" x))]))
 
   (define fxmax
     (case-lambda 
@@ -317,8 +317,8 @@
        (if (fixnum? x) 
            (if (fixnum? y) 
                (if ($fx> x y) x y)
-               (error 'fxmax "~s is not a fixnum" y))
-           (error 'fxmax "~s is not a fixnum" x))]
+               (error 'fxmax "not a fixnum" y))
+           (error 'fxmax "not a fixnum" x))]
       [(x y z . ls)
        (fxmax (fxmax x y) 
          (if (fixnum? z) 
@@ -330,9 +330,9 @@
                          (if ($fx> a z)
                              (f a ($cdr ls))
                              (f z ($cdr ls)))
-                         (error 'fxmax "~s is not a fixnum" a)))))
-             (error 'fxmax "~s is not a fixnum" z)))]
-      [(x) (if (fixnum? x) x (error 'fxmax "~s is not a fixnum" x))]))
+                         (error 'fxmax "not a fixnum" a)))))
+             (error 'fxmax "not a fixnum" z)))]
+      [(x) (if (fixnum? x) x (error 'fxmax "not a fixnum" x))]))
 
   (define (fx*/carry fx1 fx2 fx3)
     (let ([s0 ($fx+ ($fx* fx1 fx2) fx3)])
@@ -369,7 +369,7 @@
                    (values str ($fxadd1 j))))))])))
     (define fixnum->string
       (lambda (x)
-        (unless (fixnum? x) (error 'fixnum->string "~s is not a fixnum" x))
+        (unless (fixnum? x) (error 'fixnum->string "not a fixnum" x))
         (cond
           [($fxzero? x) "0"]
           [($fx> x 0) 
diff --git a/scheme/ikarus.handlers.ss b/scheme/ikarus.handlers.ss
index 606ec78..4fc12da 100644
--- a/scheme/ikarus.handlers.ss
+++ b/scheme/ikarus.handlers.ss
@@ -10,7 +10,7 @@
          [(v) (set! x v)])]
       [(x guard)
        (unless (procedure? guard)
-         (error 'make-parameter "~s is not a procedure" guard))
+         (error 'make-parameter "not a procedure" guard))
        (set! x (guard x))
        (case-lambda
          [() x]
@@ -35,20 +35,20 @@
       (lambda (x)
         (if (procedure? x)
             x
-            (error 'interrupt-handler "~s is not a procedure" x)))))
+            (error 'interrupt-handler "not a procedure" x)))))
 
   (define $apply-nonprocedure-error-handler
     (lambda (x)
-      (error 'apply "~s is not a procedure" x)))
+      (error 'apply "not a procedure" x)))
   
   (define $incorrect-args-error-handler
     (lambda (p n)
-      (error 'apply "incorrect number of argument (~s) to ~s" n p)))
+      (error 'apply "incorrect number of argument" n p)))
   
   (define $multiple-values-error
     (lambda args
       (error 'apply 
-             "incorrect number of values ~s returned to single value context" 
+             "incorrect number of values returned to single value context" 
              args)))
   
   (define $debug
@@ -64,42 +64,42 @@
       (cond
         [(symbol? x)
          (if (symbol-bound? x)
-             (error 'top-level-value-error "BUG in ~s" x)
+             (error 'top-level-value-error "BUG: should not happen" x)
              (error #f "unbound" (string->symbol (symbol->string x))))]
         [else
-         (error 'top-level-value "~s is not a symbol" x)])))
+         (error 'top-level-value "not a symbol" x)])))
   
   (define car-error
     (lambda (x)
-      (error 'car "~s is not a pair" x)))
+      (error 'car "not a pair" x)))
   
   (define cdr-error
     (lambda (x)
-      (error 'cdr "~s is not a pair" x)))
+      (error 'cdr "not a pair" x)))
   
   (define fxadd1-error
     (lambda (x)
       (if (fixnum? x)
           (error 'fxadd1 "overflow")
-          (error 'fxadd1 "~s is not a fixnum" x))))
+          (error 'fxadd1 "not a fixnum" x))))
   
   (define fxsub1-error
     (lambda (x)
       (if (fixnum? x)
           (error 'fxsub1 "underflow")
-          (error 'fxsub1 "~s is not a fixnum" x))))
+          (error 'fxsub1 "not a fixnum" x))))
   
   (define cadr-error
     (lambda (x)
-      (error 'cadr "invalid list structure in ~s" x)))
+      (error 'cadr "invalid list structure" x)))
   
   (define fx+-type-error
     (lambda (x)
-      (error 'fx+ "~s is not a fixnum" x)))
+      (error 'fx+ "not a fixnum" x)))
   
   (define fx+-types-error
     (lambda (x y)
-      (error 'fx+ "~s is not a fixnum"
+      (error 'fx+ "not a fixnum"
              (if (fixnum? x) y x))))
   
   (define fx+-overflow-error
diff --git a/scheme/ikarus.hash-tables.ss b/scheme/ikarus.hash-tables.ss
index f9fcba9..c40ca34 100644
--- a/scheme/ikarus.hash-tables.ss
+++ b/scheme/ikarus.hash-tables.ss
@@ -259,28 +259,28 @@
                 (>= k 0))
            (make-eq-hashtable)
            (error 'make-eq-hashtable
-             "invalid initial capacity ~s" k))]))
+             "invalid initial capacity" k))]))
 
   (define hashtable-ref
     (lambda (h x v)
       (if (hasht? h)
           (get-hash h x v)
-          (error 'hashtable-ref "~s is not a hash table" h))))
+          (error 'hashtable-ref "not a hash table" h))))
 
 
   (define hashtable-contains?
     (lambda (h x)
       (if (hasht? h)
           (in-hash? h x)
-          (error 'hashtable-contains? "~s is not a hash table" h))))
+          (error 'hashtable-contains? "not a hash table" h))))
 
   (define hashtable-set!
     (lambda (h x v)
       (if (hasht? h)
           (if (hasht-mutable? h) 
               (put-hash! h x v)
-              (error 'hashtable-set! "~s is immutable" h))
-          (error 'hashtable-set! "~s is not a hash table" h))))
+              (error 'hashtable-set! "hashtable is immutable" h))
+          (error 'hashtable-set! "not a hash table" h))))
 
 
   (define hashtable-update!
@@ -289,16 +289,16 @@
           (if (hasht-mutable? h)
               (if (procedure? proc)
                   (update-hash! h x proc default)
-                  (error 'hashtable-update! "~s is not a procedure" proc))
-              (error 'hashtable-update! "~s is immutable" h))
-          (error 'hashtable-update! "~s is not a hash table" h))))
+                  (error 'hashtable-update! "not a procedure" proc))
+              (error 'hashtable-update! "hashtable is immutable" h))
+          (error 'hashtable-update! "not a hash table" h))))
 
 
   (define hashtable-size
     (lambda (h)
       (if (hasht? h) 
           (hasht-count h)
-          (error 'hashtable-size "~s is not a hash table" h))))
+          (error 'hashtable-size "not a hash table" h))))
 
   (define hashtable-delete!
     (lambda (h x) 
@@ -307,23 +307,23 @@
       (if (hasht? h)
           (if (hasht-mutable? h)
               (del-hash h x)
-              (error 'hashtable-delete! "~s is immutable" h))
-          (error 'hashtable-delete! "~s is not a hash table" h))))
+              (error 'hashtable-delete! "hashtable is immutable" h))
+          (error 'hashtable-delete! "not a hash table" h))))
 
   (define (hashtable-keys h)
     (if (hasht? h) 
         (get-keys h)
-        (error 'hashtable-keys "~s is not a hash table" h)))
+        (error 'hashtable-keys "not a hash table" h)))
 
   (define (hashtable-mutable? h)
     (if (hasht? h) 
         (hasht-mutable? h)
-        (error 'hashtable-mutable? "~s is not a hash table" h)))
+        (error 'hashtable-mutable? "not a hash table" h)))
 
   (define (hashtable-clear! h)
     (if (hasht? h) 
         (if (hasht-mutable? h)
             (clear-hash! h)
-            (error 'hashtable-clear! "~s is immutable" h))
-        (error 'hashtable-clear! "~s is not a hash table" h)))
+            (error 'hashtable-clear! "hashtable is immutable" h))
+        (error 'hashtable-clear! "not a hash table" h)))
 )
diff --git a/scheme/ikarus.intel-assembler.ss b/scheme/ikarus.intel-assembler.ss
index 5da9d7c..60383a0 100644
--- a/scheme/ikarus.intel-assembler.ss
+++ b/scheme/ikarus.intel-assembler.ss
@@ -58,7 +58,7 @@
   (lambda (x)
     (cond
       [(assq x register-mapping) => caddr]
-      [else (error 'register-index "not a register ~s" x)])))
+      [else (error 'register-index "not a register" x)])))
 
 (define reg32?
   (lambda (x)
@@ -194,7 +194,7 @@
        (cons (cons 'label-addr (label-name n)) ac)]
       [(foreign? n)
        (cons (cons 'foreign-label (label-name n)) ac)]
-      [else (error 'IMM32 "invalid ~s" n)])))
+      [else (error 'IMM32 "invalid" n)])))
 
 
 (define IMM8
@@ -202,7 +202,7 @@
     (cond
       [(int? n) 
        (cons* (byte n) ac)]
-      [else (error 'IMM8 "invalid ~s" n)])))
+      [else (error 'IMM8 "invalid" n)])))
 
 
 (define imm?
@@ -229,7 +229,7 @@
        (let ([d (cdr x)])
          (unless (and (null? (cdr d))
                       (symbol? (car d)))
-           (error 'assemble "invalid label ~s" x)))
+           (error 'assemble "invalid label" x)))
        #t]
       [else #f])))
 
@@ -241,7 +241,7 @@
          (unless (and (null? (cdr d))
                       (or (symbol? (car d))
                           (string? (car d))))
-           (error 'assemble "invalid label-address ~s" x)))
+           (error 'assemble "invalid label-address" x)))
        #t]
       [else #f])))
 
@@ -265,7 +265,7 @@
        (CODE c (ModRM 1 d s (IMM8 i ac)))]
       [(imm? i)
        (CODE c (ModRM 2 d s (IMM32 i ac)))]
-      [else (error 'CODErri "invalid i=~s" i)])))
+      [else (error 'CODErri "invalid i" i)])))
 
 (define CODErr
   (lambda (c d s ac)
@@ -297,8 +297,9 @@
          (cons (reloc-word+ v d) ac))]
       [(and (int? i2) (obj? i1)) (IMM32*2 i2 i1 ac)]
       [(and (int? i1) (int? i2)) 
+       ;FIXME
        (IMM32 i1 (IMM32 i2 ac))]
-      [else (error 'assemble "IMM32*2 ~s ~s" i1 i2)])))
+      [else (error 'assemble "invalid IMM32*2" i1 i2)])))
 
 (define CODErd
   (lambda (c r1 disp ac)
@@ -315,7 +316,7 @@
            (CODE c 
              (ModRM 0 r1 '/5 
                (IMM32*2 a1 a2 ac)))]
-          [else (error 'CODErd "unhandled ~s" disp)])))))
+          [else (error 'CODErd "unhandled" disp)])))))
 
 (define CODEdi
   (lambda (c /? disp n ac)
@@ -323,14 +324,14 @@
       (lambda (a1 a2)
         (cond
           [(and (reg? a1) (reg? a2)) 
-           (error 'CODEdi "unsupported1 ~s" disp)]
+           (error 'CODEdi "unsupported1" disp)]
           [(and (imm? a1) (reg? a2))
            (CODErri c /? a2 a1 (IMM32 n ac))]
           [(and (imm? a2) (reg? a1))
            (CODErri c /? a1 a2 (IMM32 n ac))]
           [(and (imm? a1) (imm? a2))
-           (error 'CODEdi "unsupported2 ~s" disp)]
-          [else (error 'CODEdi "unhandled ~s" disp)])))))
+           (error 'CODEdi "unsupported2" disp)]
+          [else (error 'CODEdi "unhandled" disp)])))))
 
 (define (SIB s i b ac)
   (cons (byte
@@ -360,8 +361,8 @@
                (CODE c (ModRM 1 /d '/4 (SIB 0 a0 a1 (IMM8 0 ac))))]
               [(and (imm? a0) (imm? a1))
                (CODE c (ModRM 0 /d '/5 (IMM32*2 a0 a1 ac)))]
-              [else (error 'CODE/digit "unhandled ~s ~s" a0 a1)])))]
-      [else (error 'CODE/digit "unhandled ~s" dst)])))
+              [else (error 'CODE/digit "unhandled" a0 a1)])))]
+      [else (error 'CODE/digit "unhandled" dst)])))
 
 (define CODEid
   (lambda (c /? n disp ac)
@@ -369,7 +370,7 @@
       (lambda (a1 a2)
         (cond
           [(and (reg? a1) (reg? a2)) 
-           (error 'CODEid "unsupported1 ~s" disp)]
+           (error 'CODEid "unsupported1" disp)]
           [(and (imm? a1) (reg? a2))
            (error 'CODEid "unsupported2")
            (CODErri c /? a2 a1 (IMM32 n ac))]
@@ -378,7 +379,7 @@
            (CODErri c /? a1 a2 (IMM32 n ac))]
           [(and (imm? a1) (imm? a2))
            (error 'CODEid "unsupported4")]
-          [else (error 'CODEid "unhandled ~s" disp)])))))
+          [else (error 'CODEid "unhandled" disp)])))))
 
 (define CODEdi8
   (lambda (c /? disp n ac)
@@ -410,20 +411,20 @@
            [(fx= n 2)
             (if (fx= (length args) 2)
                 (proc a ac (car args) (cadr args))
-                (error 'convert-instruction "incorrect args in ~s" a))]
+                (error 'convert-instruction "incorrect args" a))]
            [(fx= n 1)
             (if (fx= (length args) 1)
                 (proc a ac (car args))
-                (error 'convert-instruction "incorrect args in ~s" a))]
+                (error 'convert-instruction "incorrect args" a))]
            [(fx= n 0)
             (if (fx= (length args) 0)
                 (proc a ac)
-                (error 'convert-instruction "incorrect args in ~s" a))] 
+                (error 'convert-instruction "incorrect args" a))] 
            [else
             (if (fx= (length args) n)
                 (apply proc a ac args)
-                (error 'convert-instruction "incorrect args in ~s" a))])))]
-    [else (error 'convert-instruction "unknown instruction in ~s" a)]))
+                (error 'convert-instruction "incorrect args" a))])))]
+    [else (error 'convert-instruction "unknown instruction" a)]))
 
 
 
@@ -433,17 +434,17 @@
      (cond
        [(reg? arg2) (CODEri ircode arg2 arg1 ac)]
        [(mem? arg2) (CODEdi imcode '/0 arg2 arg1 ac)]
-       [else (error 'instr/2 "invalid args ~s ~s" arg1 arg2)])]
+       [else (error 'instr/2 "invalid args" arg1 arg2)])]
     [(reg? arg1)
      (cond
        [(reg? arg2) (CODErr rrcode arg1 arg2 ac)]
        [(mem? arg2) (CODErd rmcode arg1 arg2 ac)]
-       [else (error 'instr/2 "invalid args ~s ~s" arg1 arg2)])]
+       [else (error 'instr/2 "invalid args" arg1 arg2)])]
     [(mem? arg1)
      (cond
        [(reg? arg2) (CODErd mrcode arg2 arg1 ac)]
-       [else (error 'instr/2 "invalid args ~s ~s" arg1 arg2)])]
-    [else (error 'instr/2 "invalid args ~s ~s" arg1 arg2)]))
+       [else (error 'instr/2 "invalid args" arg1 arg2)])]
+    [else (error 'instr/2 "invalid args" arg1 arg2)]))
 
 (module ()
 (define who 'assembler)
@@ -452,7 +453,7 @@
   (cond
     [(reg8? dst)
      (CODE #x0F (CODE c (ModRM 3 '/0 dst ac)))]
-    [else (error who "invalid condition-set to ~s" dst)]))
+    [else (error who "invalid condition-set" dst)]))
 
 (define (conditional-jump c dst ac)
   (cond
@@ -460,7 +461,7 @@
      (CODE #x0F (CODE c (IMM32 dst ac)))]
     [(label? dst)
      (CODE #x0F (CODE c (cons (cons 'relative (label-name dst)) ac)))]
-    [else (error who "invalid conditional jump target ~s" dst)]))
+    [else (error who "invalid conditional jump target" dst)]))
 
 (add-instructions instr ac
    [(ret)  (CODE #xC3 ac)]
@@ -473,46 +474,46 @@
        ((CODE/digit #xC6 '/0) dst (IMM8 src ac))]
       [(and (reg8? src) (mem? dst)) (CODErd #x88 src dst ac)]
       [(and (mem? src) (reg8? dst)) (CODErd #x8A dst src ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(movsd src dst)
     (cond
       [(and (xmmreg? dst) (or (xmmreg? src) (mem? src)))
        (CODE #xF2 (CODE #x0F ((CODE/digit #x10 dst) src ac)))]
       [(and (xmmreg? src) (or (xmmreg? dst) (mem? dst)))
        (CODE #xF2 (CODE #x0F ((CODE/digit #x11 src) dst ac)))]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(cvtsi2sd src dst)
     (cond
       [(and (xmmreg? dst) (reg? src))
        (CODE #xF2 (CODE #x0F (CODE #x2A (ModRM 3 src dst ac))))]
       [(and (xmmreg? dst) (mem? src))
        (CODE #xF2 (CODE #x0F ((CODE/digit #x2A dst) src ac)))]
-      [else (error who "invalid ~s" instr)])] 
+      [else (error who "invalid" instr)])] 
    [(addsd src dst)
     (cond
       [(and (xmmreg? dst) (or (xmmreg? src) (mem? src)))
        (CODE #xF2 (CODE #x0F ((CODE/digit #x58 dst) src ac)))]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(subsd src dst)
     (cond
       [(and (xmmreg? dst) (or (xmmreg? src) (mem? src)))
        (CODE #xF2 (CODE #x0F ((CODE/digit #x5C dst) src ac)))]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(mulsd src dst)
     (cond
       [(and (xmmreg? dst) (or (xmmreg? src) (mem? src)))
        (CODE #xF2 (CODE #x0F ((CODE/digit #x59 dst) src ac)))]
-      [else (error who "invalid ~s" instr)])] 
+      [else (error who "invalid" instr)])] 
    [(divsd src dst)
     (cond
       [(and (xmmreg? dst) (or (xmmreg? src) (mem? src)))
        (CODE #xF2 (CODE #x0F ((CODE/digit #x5E dst) src ac)))]
-      [else (error who "invalid ~s" instr)])] 
+      [else (error who "invalid" instr)])] 
    [(ucomisd src dst)
     (cond
       [(and (xmmreg? dst) (or (xmmreg? src) (mem? src)))
        (CODE #x66 (CODE #x0F ((CODE/digit #x2E dst) src ac)))]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(addl src dst)
     (cond   
       [(and (imm8? src) (reg? dst)) 
@@ -529,7 +530,7 @@
        ((CODE/digit #x81 '/0) dst (IMM32 src ac))]
       [(and (reg? src) (mem? dst))
        ((CODE/digit #x01 src) dst ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(subl src dst)
     (cond   
       [(and (imm8? src) (reg? dst)) 
@@ -546,7 +547,7 @@
        ((CODE/digit #x81 '/5) dst (IMM32 src ac))]
       [(and (reg? src) (mem? dst))
        ((CODE/digit #x29 src) dst ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(sall src dst)
     (cond
       [(and (equal? 1 src) (reg? dst))
@@ -559,7 +560,7 @@
        (CODE #xD3 (ModRM 3 '/4 dst ac))]
       [(and (eq? src '%cl) (mem? dst))
        ((CODE/digit #xD3 '/4) dst ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(shrl src dst)
     (cond
       [(and (equal? 1 src) (reg? dst))
@@ -572,7 +573,7 @@
        ((CODE/digit #xC1 '/5) dst (IMM8 src ac))]
       [(and (eq? src '%cl) (mem? dst))
        ((CODE/digit #xD3 '/5) dst ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(sarl src dst)
     (cond
       [(and (equal? 1 src) (reg? dst))
@@ -585,7 +586,7 @@
        (CODE #xD3 (ModRM 3 '/7 dst ac))]
       [(and (eq? src '%cl) (mem? dst))
        ((CODE/digit #xD3 '/7) dst ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(andl src dst) 
     (cond
       [(and (imm? src) (mem? dst))
@@ -602,7 +603,7 @@
        ((CODE/digit #x21 src) dst ac)]
       [(and (mem? src) (reg? dst))
        (CODErd #x23 dst src ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(orl src dst) 
     (cond
       [(and (imm? src) (mem? dst))
@@ -619,7 +620,7 @@
        (CODE #x09 (ModRM 3 src dst ac))]
       [(and (mem? src) (reg? dst))
        (CODErd #x0B dst src ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(xorl src dst) 
     (cond
       [(and (imm8? src) (reg? dst)) 
@@ -630,12 +631,12 @@
        (CODE #x31 (ModRM 3 src dst ac))]
       [(and (mem? src) (reg? dst))
        (CODErd #x33 dst src ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(leal src dst) 
     (cond
       [(and (mem? src) (reg? dst))
        (CODErd #x8D dst src ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(cmpl src dst)
     (cond
       [(and (imm8? src) (reg? dst)) 
@@ -654,7 +655,7 @@
       [(and (imm? src) (mem? dst))
        ;;; maybe error 
        (CODErd #x81 '/7 dst (IMM32 src ac))]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(imull src dst)
     (cond
       [(and (imm8? src) (reg? dst)) 
@@ -665,7 +666,7 @@
        (CODE #x0F (CODE #xAF (ModRM 3 dst src ac)))]
       [(and (mem? src) (reg? dst))
        (CODE #x0F (CODErd #xAF dst src ac))]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(idivl dst)
     (cond
       [(reg? dst)
@@ -673,7 +674,7 @@
       [(mem? dst)
        ;;; maybe error 
        (CODErd #xF7 '/7 dst ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(pushl dst)
     (cond
       [(imm8? dst) 
@@ -685,7 +686,7 @@
       [(mem? dst)
        ;;; maybe error 
        (CODErd #xFF '/6 dst ac)]
-      [else (error who "invalid ~s" instr)])] 
+      [else (error who "invalid" instr)])] 
    [(popl dst)
     (cond
       [(reg? dst)
@@ -693,7 +694,7 @@
       [(mem? dst)
        ;;; maybe error 
        (CODErd #x8F '/0 dst ac)]
-      [else (error who "invalid ~s" instr)])] 
+      [else (error who "invalid" instr)])] 
    [(notl dst)
     (cond
       [(reg? dst)
@@ -701,12 +702,12 @@
       [(mem? dst)
        ;;; maybe error 
        (CODErd #xF7 '/7 dst ac)]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(negl dst)
     (cond
       [(reg? dst)
        (CODE #xF7 (ModRM 3 '/3 dst ac))]
-      [else (error who "invalid ~s" instr)])]
+      [else (error who "invalid" instr)])]
    [(jmp dst)
     (cond
       [(label? dst)
@@ -716,7 +717,7 @@
       [(mem? dst)
        ;;; maybe error 
        (CODErd #xFF '/4 dst ac)]
-      [else (error who "invalid jmp target ~s" dst)])]
+      [else (error who "invalid jmp target" dst)])]
    [(call dst)
     (cond
       [(imm? dst) 
@@ -728,7 +729,7 @@
        (CODErd #xFF '/2 dst ac)]
       [(reg? dst)
        (CODE #xFF (ModRM 3 '/2 dst ac))]
-      [else (error who "invalid jmp target ~s" dst)])]
+      [else (error who "invalid jmp target" dst)])]
    [(seta dst)   (conditional-set  #x97 dst ac)]
    [(setae dst)  (conditional-set  #x93 dst ac)]
    [(setb dst)   (conditional-set  #x92 dst ac)]
@@ -769,15 +770,15 @@
    [(jp dst)     (conditional-jump #x8A dst ac)]
    [(jnp dst)    (conditional-jump #x8B dst ac)]
    [(byte x)
-    (unless (byte? x) (error who "~s is not a byte" x))
+    (unless (byte? x) (error who "not a byte" x))
     (cons (byte x) ac)]
    [(byte-vector x) (append (map (lambda (x) (byte x)) (vector->list x)) ac)]
    [(int a) (IMM32 a ac)]
    [(label L)
-    (unless (symbol? L) (error who "label ~s is not a symbol" L))
+    (unless (symbol? L) (error who "label is not a symbol" L))
     (cons (cons 'label L) ac)]
    [(label-address L)
-    (unless (symbol? L) (error who "label-address ~s is not a symbol" L))
+    (unless (symbol? L) (error who "label-address is not a symbol" L))
     (cons (cons 'label-addr L) ac)]
    [(current-frame-offset)
     (cons '(current-frame-offset) ac)]
@@ -797,7 +798,7 @@
                     relative local-relative current-frame-offset)
                    (fx+ ac 4)]
                   [(label) ac]
-                  [else (error 'compute-code-size "unknown instr ~s" x)])))
+                  [else (error 'compute-code-size "unknown instr" x)])))
           0 
           ls)))
 
@@ -805,13 +806,13 @@
 (define set-label-loc!
   (lambda (x loc)
     (when (getprop x '*label-loc*)
-      (error 'compile "label ~s is already defined" x))
+      (error 'compile "label is already defined" x))
     (putprop x '*label-loc* loc)))
 
 (define label-loc
   (lambda (x)
     (or (getprop x '*label-loc*)
-        (error 'compile "undefined label ~s" x))))
+        (error 'compile "undefined label" x))))
 
 
 (define unset-label-loc!
@@ -827,7 +828,7 @@
        (code-set! code (fx+ idx 1) (fxlogand (fxsra x 6) #xFF))
        (code-set! code (fx+ idx 2) (fxlogand (fxsra x 14) #xFF))
        (code-set! code (fx+ idx 3) (fxlogand (fxsra x 22) #xFF))]
-      [else (error 'set-code-word! "unhandled ~s" x)])))
+      [else (error 'set-code-word! "unhandled" x)])))
  
 (define (optimize-local-jumps ls)
   (define locals '())
@@ -881,7 +882,7 @@
                    (set-label-loc! (cdr a) (list x idx))
                    (f (cdr ls) idx reloc)]
                   [else
-                   (error 'whack-instructions "unknown instr ~s" a)])))])))
+                   (error 'whack-instructions "unknown instr" a)])))])))
     (f ls 0 '())))
 
 (define wordsize 4)
@@ -896,7 +897,7 @@
                   [(reloc-word foreign-label)        (fx+ ac 2)]
                   [(relative reloc-word+ label-addr) (fx+ ac 3)]
                   [(word byte label current-frame-offset local-relative) ac]
-                  [else (error 'compute-reloc-size "unknown instr ~s" x)])))
+                  [else (error 'compute-reloc-size "unknown instr" x)])))
           0 
           ls)))
 
@@ -923,7 +924,6 @@
   (lambda (thunk?-label code vec)
     (define reloc-idx 0)
     (lambda (r)
-      ;(printf "r=~s\n" r)
       (let ([idx (car r)] [type (cadr r)]
             [v 
              (let ([v (cddr r)])
@@ -936,7 +936,7 @@
                          (let ([code (car p)] [idx (cadr p)])
                            (unless (fx= idx 0)
                              (error 'whack-reloc 
-                               "cannot create a thunk pointing at ~s"
+                               "cannot create a thunk pointing"
                                idx))
                            (let ([thunk (code->thunk code)])
                              (set-cdr! (cdr p) (list thunk))
@@ -954,7 +954,7 @@
            (let ([name 
                   (if (string? v)
                       (foreign-string->bytevector v)
-                      (error 'whack-reloc "not a string ~s" v))])
+                      (error 'whack-reloc "not a string" v))])
              (vector-set! vec reloc-idx (fxlogor 1 (fxsll idx 2)))
              (vector-set! vec (fx+ reloc-idx 1) name)
              (set! reloc-idx (fx+ reloc-idx 2)))]
@@ -986,14 +986,13 @@
            (let ([loc (label-loc v)])
              (let ([obj (car loc)] [disp (cadr loc)])
                (unless (and (code? obj) (fixnum? disp))
-                 (error 'whack-reloc "invalid relative jump obj=~s  disp=~s\n" 
-                        obj disp))
+                 (error 'whack-reloc "invalid relative jump obj/disp" obj disp))
                (vector-set! vec reloc-idx (fxlogor 3 (fxsll idx 2)))
                (vector-set! vec (fx+ reloc-idx 1) 
                  (fx+ disp (code-entry-adjustment)))
                (vector-set! vec (fx+ reloc-idx 2) obj)))
            (set! reloc-idx (fx+ reloc-idx 3))]
-          [else (error 'whack-reloc "invalid reloc type ~s" type)]))
+          [else (error 'whack-reloc "invalid reloc type" type)]))
       )))
 
 
@@ -1034,9 +1033,6 @@
                   (lambda (foo reloc*)
                     (for-each (whack-reloc thunk?-label (car foo) (cdr foo)) reloc*))
                   (map cons code* relv*) reloc**)
-                ;(for-each (lambda (x)
-                ;            (printf "RV=~s\n" x))
-                ;          relv*)
                 (for-each set-code-reloc-vector! code* relv*)
                 (for-each (lambda (code name)
                             (when name
diff --git a/scheme/ikarus.io-ports.ss b/scheme/ikarus.io-ports.ss
index 4db64b7..14f336b 100644
--- a/scheme/ikarus.io-ports.ss
+++ b/scheme/ikarus.io-ports.ss
@@ -51,8 +51,8 @@
       (if (procedure? handler)
           (if (bytevector? buffer)
               ($make-input-port handler buffer)
-              (error 'make-input-port "~s is not a bytevector" buffer))
-          (error 'make-input-port "~s is not a procedure" handler))))
+              (error 'make-input-port "not a bytevector" buffer))
+          (error 'make-input-port "not a procedure" handler))))
   ;;;
   (define $make-output-port
     (lambda (handler buffer)
@@ -63,50 +63,50 @@
       (if (procedure? handler)
           (if (bytevector? buffer)
               ($make-output-port handler buffer)
-              (error 'make-output-port "~s is not a bytevector" buffer))
-          (error 'make-output-port "~s is not a procedure" handler))))
+              (error 'make-output-port "not a bytevector" buffer))
+          (error 'make-output-port "not a procedure" handler))))
   ;;;
   (define port-handler
     (lambda (x)
       (if (port? x)
           ($port-handler x)
-          (error 'port-handler "~s is not a port" x))))
+          (error 'port-handler "not a port" x))))
   ;;;
   (define port-input-buffer
     (lambda (x)
       (if (input-port? x)
           ($port-buffer x)
-          (error 'port-input-buffer "~s is not an input-port" x))))
+          (error 'port-input-buffer "not an input-port" x))))
   ;;;
   (define port-input-index
     (lambda (x)
       (if (input-port? x)
           ($port-index x)
-          (error 'port-input-index "~s is not an input-port" x))))
+          (error 'port-input-index "not an input-port" x))))
   ;;;
   (define port-input-size
     (lambda (x)
       (if (input-port? x)
           ($port-size x)
-          (error 'port-input-size "~s is not an input-port" x))))
+          (error 'port-input-size "not an input-port" x))))
   ;;;
   (define port-output-buffer
     (lambda (x)
       (if (output-port? x)
           ($port-buffer x)
-          (error 'port-output-buffer "~s is not an output-port" x))))
+          (error 'port-output-buffer "not an output-port" x))))
   ;;;
   (define port-output-index
     (lambda (x)
       (if (output-port? x)
           ($port-index x)
-          (error 'port-output-index "~s is not an output-port" x))))
+          (error 'port-output-index "not an output-port" x))))
   ;;;
   (define port-output-size
     (lambda (x)
       (if (output-port? x)
           ($port-size x)
-          (error 'port-output-size "~s is not an output-port" x))))
+          (error 'port-output-size "not an output-port" x))))
   ;;;
   (define set-port-input-index!
     (lambda (p i)
@@ -115,10 +115,10 @@
               (if ($fx>= i 0)
                   (if ($fx<= i ($port-size p))
                       ($set-port-index! p i)
-                      (error 'set-port-input-index! "index ~s is too big" i))
-                  (error 'set-port-input-index! "index ~s is negative" i))
-              (error 'set-port-input-index! "~s is not a valid index" i))
-          (error 'set-port-input-index! "~s is not an input-port" p))))
+                      (error 'set-port-input-index! "index is too big" i))
+                  (error 'set-port-input-index! "index is negative" i))
+              (error 'set-port-input-index! "not a valid index" i))
+          (error 'set-port-input-index! "not an input-port" p))))
   ;;;
   (define set-port-input-size!
     (lambda (p i)
@@ -129,10 +129,10 @@
                       (begin
                         ($set-port-index! p 0)
                         ($set-port-size! p i))
-                      (error 'set-port-input-size! "size ~s is too big" i))
-                  (error 'set-port-input-size! "size ~s is negative" i))
-              (error 'set-port-input-size! "~s is not a valid size" i))
-          (error 'set-port-input-size! "~s is not an input-port" p))))
+                      (error 'set-port-input-size! "size is too big" i))
+                  (error 'set-port-input-size! "size is negative" i))
+              (error 'set-port-input-size! "not a valid size" i))
+          (error 'set-port-input-size! "not an input-port" p))))
   ;;;
   (define set-port-output-index!
     (lambda (p i)
@@ -141,10 +141,10 @@
               (if ($fx>= i 0)
                   (if ($fx<= i ($port-size p))
                       ($set-port-index! p i)
-                      (error 'set-port-output-index! "index ~s is too big" i))
-                  (error 'set-port-output-index! "index ~s is negative" i))
-              (error 'set-port-output-index! "~s is not a valid index" i))
-          (error 'set-port-output-index! "~s is not an output-port" p))))
+                      (error 'set-port-output-index! "index is too big" i))
+                  (error 'set-port-output-index! "index is negative" i))
+              (error 'set-port-output-index! "not a valid index" i))
+          (error 'set-port-output-index! "not an output-port" p))))
   ;;;
   (define set-port-output-size!
     (lambda (p i)
@@ -155,10 +155,10 @@
                       (begin
                         ($set-port-index! p 0)
                         ($set-port-size! p i))
-                      (error 'set-port-output-size! "size ~s is too big" i))
-                  (error 'set-port-output-size! "size ~s is negative" i))
-              (error 'set-port-output-size! "~s is not a valid size" i))
-          (error 'set-port-output-size! "~s is not an output-port" p)))))
+                      (error 'set-port-output-size! "size is too big" i))
+                  (error 'set-port-output-size! "size is negative" i))
+              (error 'set-port-output-size! "not a valid size" i))
+          (error 'set-port-output-size! "not an output-port" p)))))
 
 
 
diff --git a/scheme/ikarus.io-primitives.ss b/scheme/ikarus.io-primitives.ss
index 11e8492..f8be0ae 100644
--- a/scheme/ikarus.io-primitives.ss
+++ b/scheme/ikarus.io-primitives.ss
@@ -19,26 +19,26 @@
       [(c)
        (if (char? c)
            ($write-char c (current-output-port))
-           (error 'write-char "~s is not a character" c))]
+           (error 'write-char "not a character" c))]
       [(c p)
        (if (char? c)
            (if (output-port? p)
                ($write-char c p)
-               (error 'write-char "~s is not an output-port" p))
-           (error 'write-char "~s is not a character" c))]))
+               (error 'write-char "not an output-port" p))
+           (error 'write-char "not a character" c))]))
    
   (define write-byte
     (case-lambda
       [(b)
        (if (and (fixnum? b) ($fx<= 0 b) ($fx<= b 255))
            ($write-byte b (current-output-port))
-           (error 'write-byte "~s is not a byte" b))]
+           (error 'write-byte "not a byte" b))]
       [(b p)
        (if (and (fixnum? b) ($fx<= 0 b) ($fx<= b 255))
            (if (output-port? p)
                ($write-byte b p)
-               (error 'write-byte "~s is not an output-port" p))
-           (error 'write-byte "~s is not a byte" b))]))
+               (error 'write-byte "not an output-port" p))
+           (error 'write-byte "not a byte" b))]))
   ;;;
   (define newline
     (case-lambda
@@ -50,25 +50,25 @@
            (begin
              ($write-char #\newline p)
              ($flush-output-port p))
-           (error 'newline "~s is not an output port" p))]))
+           (error 'newline "not an output port" p))]))
   ;;;
   (define port-name
     (lambda (p)
       (if (port? p) 
           (($port-handler p) 'port-name p)
-          (error 'port-name "~s is not a port" p))))
+          (error 'port-name "not a port" p))))
 
   (define input-port-name
     (lambda (p)
       (if (port? p) 
           (($port-handler p) 'port-name p)
-          (error 'input-port-name "~s is not a port" p))))
+          (error 'input-port-name "not a port" p))))
 
   (define output-port-name
     (lambda (p)
       (if (port? p) 
           (($port-handler p) 'port-name p)
-          (error 'output-port-name "~s is not a port" p))))
+          (error 'output-port-name "not a port" p))))
 
   (define read-char
     (case-lambda
@@ -76,19 +76,19 @@
       [(p)
        (if (input-port? p)
            ($read-char p)
-           (error 'read-char "~s is not an input-port" p))]))
+           (error 'read-char "not an input-port" p))]))
   ;;;
   (define unread-char
     (case-lambda
       [(c) (if (char? c)
                ($unread-char c (current-input-port))
-               (error 'unread-char "~s is not a character" c))]
+               (error 'unread-char "not a character" c))]
       [(c p)
        (if (input-port? p)
            (if (char? c)
                ($unread-char c p)
-               (error 'unread-char "~s is not a character" c))
-           (error 'unread-char "~s is not an input-port" p))]))
+               (error 'unread-char "not a character" c))
+           (error 'unread-char "not an input-port" p))]))
   ;;;
   (define peek-char
     (case-lambda
@@ -96,7 +96,7 @@
       [(p)
        (if (input-port? p)
            ($peek-char p)
-           (error 'peek-char "~s is not an input-port" p))]))
+           (error 'peek-char "not an input-port" p))]))
   ;;;
   (define reset-input-port!
     (case-lambda
@@ -104,7 +104,7 @@
       [(p)
        (if (input-port? p)
            ($reset-input-port! p)
-           (error 'reset-input-port! "~s is not an input-port" p))]))
+           (error 'reset-input-port! "not an input-port" p))]))
   ;;;
   (define close-input-port
     (case-lambda
@@ -112,7 +112,7 @@
       [(p)
        (if (input-port? p)
            ($close-input-port p)
-           (error 'close-input-port! "~s is not an input-port" p))]))
+           (error 'close-input-port! "not an input-port" p))]))
   ;;;
   (define close-output-port
     (case-lambda
@@ -120,7 +120,7 @@
       [(p)
        (if (output-port? p)
            ($close-output-port p)
-           (error 'close-output-port "~s is not an output-port" p))]))
+           (error 'close-output-port "not an output-port" p))]))
   ;;;
   (define flush-output-port
     (case-lambda
@@ -128,5 +128,5 @@
       [(p)
        (if (output-port? p)
            ($flush-output-port p)
-           (error 'flush-output-port "~s is not an output-port" p))])))
+           (error 'flush-output-port "not an output-port" p))])))
 
diff --git a/scheme/ikarus.io.input-files.ss b/scheme/ikarus.io.input-files.ss
index 2ec2d90..c812314 100644
--- a/scheme/ikarus.io.input-files.ss
+++ b/scheme/ikarus.io.input-files.ss
@@ -26,12 +26,12 @@
              [(__ y () body)
               (if (null? y) 
                   body
-                  (error 'message-case "unmatched ~s" (cons tmsg targs)))]
+                  (error 'message-case "unmatched" (cons tmsg targs)))]
              [(__ y (a a* (... ...)) body)
               (if (pair? y)
                   (let ([a (car y)] [d (cdr y)])
                     (match-and-bind d (a* (... ...)) body))
-                  (error 'message-case "unmatched ~s" (cons tmsg targs)))]))
+                  (error 'message-case "unmatched" (cons tmsg targs)))]))
          (case tmsg
            [(msg-name) 
             (match-and-bind targs (msg-arg* ...) (begin b b* ...))] ...
@@ -64,14 +64,14 @@
                        ($port-buffer p)
                        ($fxadd1 idx))])
              (unless ($fx= ($fxlogand b1 #b11000000) #b10000000)
-               (error 'read-char "invalid utf8 sequence ~a ~a" b0 b1))
+               (error 'read-char "invalid utf8 sequence" b0 b1))
              ($set-port-index! p ($fx+ idx 2))
              ($fixnum->char 
                ($fx+ ($fxsll ($fxlogand b0 #b11111) 6)
                      ($fxlogand b1 #b111111))))]
           [else 
            (error 'read-multibyte
-             "bytesequence ~a is not supported yet" b0)]))))
+             "BUG: bytesequence is not supported yet" b0)]))))
 
   (define peek-multibyte-char 
     (lambda (p)
@@ -87,7 +87,7 @@
           (message-case msg args
             [(read-char p)
              (unless (input-port? p)
-               (error 'read-char "~s is not an input port" p))
+               (error 'read-char "not an input port" p))
              (let ([idx ($port-index p)])
                (if ($fx< idx ($port-size p))
                    (let ([b ($bytevector-u8-ref ($port-buffer p) idx)])
@@ -107,12 +107,12 @@
                            [($fx= bytes 0)
                             (eof-object)]
                            [else
-                            (error 'read-char "Cannot read from ~a"
+                            (error 'read-char "Cannot read from file"
                                    port-name)]))
-                       (error 'read-char "port ~s is closed" p))))]
+                       (error 'read-char "port is closed" p))))]
             [(peek-char p)
              (unless (input-port? p)
-               (error 'peek-char "~s is not an input port" p))
+               (error 'peek-char "not an input port" p))
              (let ([idx ($port-index p)])
                (if ($fx< idx ($port-size p))
                    (let ([b ($bytevector-u8-ref ($port-buffer p) idx)])
@@ -126,20 +126,20 @@
                          (cond
                            [(not bytes)
                             (error 'peek-char
-                                   "Cannot read from ~s" port-name)]
+                                   "Cannot read from file" port-name)]
                            [($fx= bytes 0)
                             (eof-object)]
                            [else
                             ($set-port-size! p bytes)
                             ($peek-char p)]))
-                       (error 'peek-char "port ~s is closed" p))))]
+                       (error 'peek-char "port is closed" p))))]
             [(unread-char c p)
              (unless (input-port? p)
-               (error 'unread-char "~s is not an input port" p))
+               (error 'unread-char "not an input port" p))
              (let ([idx ($fxsub1 ($port-index p))]
                    [b (if (char? c) 
                           ($char->fixnum c)
-                          (error 'unread-char "~s is not a char" c))])
+                          (error 'unread-char "not a char" c))])
                (if (and ($fx>= idx 0)
                         ($fx< idx ($port-size p)))
                    (cond
@@ -147,20 +147,20 @@
                       ($set-port-index! p idx)]
                      [else (unread-multibyte-char c p)])
                    (if open?
-                       (error 'unread-char "port ~s is closed" p)
+                       (error 'unread-char "port is closed" p)
                        (error 'unread-char "too many unread-chars"))))]
             [(port-name p) port-name]
             [(close-port p)
              (unless (input-port? p)
-               (error 'close-input-port "~s is not an input port" p))
+               (error 'close-input-port "not an input port" p))
              (when open?
                ($set-port-size! p 0)
                (set! open? #f)
                (unless (foreign-call "ikrt_close_file" fd)
-                  (error 'close-input-port "cannot close ~s" port-name)))]
+                  (error 'close-input-port "cannot close port" port-name)))]
             [else 
              (error 'input-file-handler
-                    "message not handled ~s" (cons msg args))])))))
+                    "message not handled" (cons msg args))])))))
 
   (define $open-input-file
     (lambda (filename)
@@ -174,20 +174,21 @@
               (set-port-input-size! port 0)
               (guardian port)
               port)
-            (error 'open-input-file "cannot open ~s: ~a" filename fd/error)))))
+            (error 'open-input-file "cannot open file" 
+                   filename fd/error)))))
 
   (define open-input-file
     (lambda (filename)
        (if (string? filename)
            ($open-input-file filename)
-           (error 'open-input-file "~s is not a string" filename))))
+           (error 'open-input-file "not a string" filename))))
 
   (define with-input-from-file
      (lambda (name proc)
        (unless (string? name) 
-         (error 'with-input-from-file "~s is not a string" name))
+         (error 'with-input-from-file "not a string" name))
        (unless (procedure? proc)
-         (error 'with-input-from-file "~s is not a procedure" proc))
+         (error 'with-input-from-file "not a procedure" proc))
        (let ([p ($open-input-file name)])
          (call-with-values 
            (lambda () 
@@ -202,9 +203,9 @@
   (define call-with-input-file
      (lambda (name proc)
        (unless (string? name) 
-         (error 'call-with-input-file "~s is not a string" name))
+         (error 'call-with-input-file "not a string" name))
        (unless (procedure? proc)
-         (error 'call-with-input-file "~s is not a procedure" proc))
+         (error 'call-with-input-file "not a procedure" proc))
        (let ([p ($open-input-file name)])
          (call-with-values (lambda () (proc p))
             (case-lambda
@@ -225,7 +226,7 @@
       [(p) 
        (if (input-port? p)
            (set! *current-input-port* p)
-           (error 'current-input-port "~s is not an input-port" p))]))
+           (error 'current-input-port "not an input-port" p))]))
 
   (set! *standard-input-port* 
     (let ([p (make-input-port 
diff --git a/scheme/ikarus.io.input-strings.ss b/scheme/ikarus.io.input-strings.ss
index b48c38b..839ff45 100644
--- a/scheme/ikarus.io.input-strings.ss
+++ b/scheme/ikarus.io.input-strings.ss
@@ -21,12 +21,12 @@
              [(__ y () body)
               (if (null? y) 
                   body
-                  (error 'message-case "unmatched ~s" (cons tmsg targs)))]
+                  (error 'message-case "unmatched" (cons tmsg targs)))]
              [(__ y (a a* (... ...)) body)
               (if (pair? y)
                   (let ([a (car y)] [d (cdr y)])
                     (match-and-bind d (a* (... ...)) body))
-                  (error 'message-case "unmatched ~s" (cons tmsg targs)))]))
+                  (error 'message-case "unmatched" (cons tmsg targs)))]))
          (case tmsg
            [(msg-name) 
             (match-and-bind targs (msg-arg* ...) (begin b b* ...))] ...
@@ -44,20 +44,20 @@
                    c)
                  (if open?
                      (eof-object)
-                     (error 'read-char "port ~s is closed" p)))]
+                     (error 'read-char "port is closed" p)))]
             [(peek-char p)
              (if ($fx< idx n)
                  ($string-ref str idx)
                  (if open?
                      (eof-object)
-                     (error 'peek-char "port ~s is closed" p)))]
+                     (error 'peek-char "port is closed" p)))]
             [(unread-char c p)
              (let ([i ($fxsub1 idx)])
                (if (and ($fx>= i 0)
                         ($fx< i n))
                    (set! idx i)
                    (if open?
-                       (error 'unread-char "port ~s is closed" p)
+                       (error 'unread-char "port is closed" p)
                        (error 'unread-char "too many unread-chars"))))]
             [(port-name p) '*string-port*]
             [(close-port p)
@@ -65,12 +65,12 @@
                (set! open? #f))]
             [else 
              (error 'input-string-handler
-                    "message not handled ~s" (cons msg args))]))))) 
+                    "message not handled" (cons msg args))]))))) 
 
   (define open-input-string
     (lambda (str)
       (unless (string? str)
-        (error 'open-input-string "~s is not a string" str))
+        (error 'open-input-string "not a string" str))
       (let ([port (make-input-port
                     (make-input-string-handler str)
                     '#vu8())])
@@ -80,9 +80,9 @@
   (define with-input-from-string
      (lambda (str proc)
        (unless (string? str) 
-         (error 'with-input-from-string "~s is not a string" str))
+         (error 'with-input-from-string "not a string" str))
        (unless (procedure? proc)
-         (error 'with-input-from-string "~s is not a procedure" proc))
+         (error 'with-input-from-string "not a procedure" proc))
        (let ([p (open-input-string str)])
          (parameterize ([current-input-port p])
            (proc)))))
diff --git a/scheme/ikarus.io.output-files.ss b/scheme/ikarus.io.output-files.ss
index abf3b65..b81c6a3 100644
--- a/scheme/ikarus.io.output-files.ss
+++ b/scheme/ikarus.io.output-files.ss
@@ -30,12 +30,12 @@
              [(__ y () body)
               (if (null? y) 
                   body
-                  (error 'message-case "unmatched ~s" (cons tmsg targs)))]
+                  (error 'message-case "unmatched" (cons tmsg targs)))]
              [(__ y (a a* (... ...)) body)
               (if (pair? y)
                   (let ([a (car y)] [d (cdr y)])
                     (match-and-bind d (a* (... ...)) body))
-                  (error 'message-case "unmatched ~s" (cons tmsg targs)))]))
+                  (error 'message-case "unmatched" (cons tmsg targs)))]))
          (case tmsg
            [(msg-name) 
             (match-and-bind targs (msg-arg* ...) (begin b b* ...))] ...
@@ -51,22 +51,12 @@
            (close-output-port p)
            (close-ports))])))
 
-  (define do-write-buffer-old
-    (lambda (fd port-name p caller)
-      (let ([bytes (foreign-call "ikrt_write_file" 
-                                 fd
-                                 (port-output-buffer p)
-                                 (port-output-index p))])
-        (if (fixnum? bytes)
-            (set-port-output-index! p 0)
-            (error caller "cannot write to file ~s: ~a" port-name bytes)))))
-  
   (define do-write-buffer
     (lambda (fd port-name buff idx caller)
       (let ([bytes (foreign-call "ikrt_write_file" fd buff idx)])
         (if (fixnum? bytes)
             bytes
-            (error caller "cannot write to file ~s: ~a" port-name bytes)))))
+            (error caller "cannot write to file" port-name bytes)))))
 
   (define make-output-file-handler
     (lambda (fd port-name)
@@ -87,18 +77,19 @@
                                              ($port-buffer p) idx 'write-char)])
                                ($set-port-index! p 0)
                                ($write-byte b p))
-                             (error 'write-byte "port ~s is closed" p))))
-                     (error 'write-byte "~s is not an output-port" p))
-                 (error 'write-byte "~s is not a byte" b))]
+                             (error 'write-byte "port is closed" p))))
+                     (error 'write-byte "not an output-port" p))
+                 (error 'write-byte "not a byte" b))]
             [(write-char c p)
              (if (char? c)
                  (if (output-port? p)
                      (let ([b ($char->fixnum c)])
                        (if ($fx<= b 255)
                            ($write-byte b p)
-                           (error 'write-char "multibyte write of ~s not implemented" c)))
-                     (error 'write-char "~s is not an output-port" p))
-                 (error 'write-char "~s is not a character" c))]
+                           (error 'write-char 
+                              "BUG: multibyte write of not implemented" c)))
+                     (error 'write-char "not an output-port" p))
+                 (error 'write-char "not a character" c))]
             [(flush-output-port p)
              (if (output-port? p)
                  (if open?
@@ -107,18 +98,18 @@
                                      ($port-index p) 
                                      'flush-output-port)])
                        ($set-port-index! p 0))
-                     (error 'flush-output-port "port ~s is closed" p))
-                 (error 'flush-output-port "~s is not an output-port" p))]
+                     (error 'flush-output-port "port is closed" p))
+                 (error 'flush-output-port "not an output-port" p))]
             [(close-port p)
              (when open?
                (flush-output-port p)
                ($set-port-size! p 0)
                (set! open? #f)
                (unless (foreign-call "ikrt_close_file" fd)
-                 (error 'close-output-port "cannot close ~s" port-name)))]
+                 (error 'close-output-port "cannot close" port-name)))]
             [(port-name p) port-name]
             [else (error 'output-file-handler 
-                         "unhandled message ~s" (cons msg args))])))
+                         "unhandled message" (cons msg args))])))
       output-file-handler))
   (define (option-id x)
     (case x
@@ -126,7 +117,7 @@
       [(replace)  1]
       [(truncate) 2]
       [(append)   3]
-      [else (error 'open-output-file "~s is not a valid mode" x)]))
+      [else (error 'open-output-file "not a valid mode" x)]))
 
   (define $open-output-file
     (lambda (filename options)
@@ -142,7 +133,7 @@
                      ($make-bytevector 4096))])
               (guardian port)
               port)
-            (error 'open-output-file "cannot open ~s: ~a" filename fd/error)))))
+            (error 'open-output-file "cannot open file" filename fd/error)))))
 
   (define *standard-output-port* #f)
   
@@ -165,25 +156,25 @@
        [(p)
         (if (output-port? p)
             (set! *current-output-port* p)
-            (error 'current-output-port "~s is not an output port" p))]))
+            (error 'current-output-port "not an output port" p))]))
 
   (define open-output-file 
     (case-lambda
       [(filename)
        (if (string? filename)
            ($open-output-file filename 'error)
-           (error 'open-output-file "~s is not a string" filename))]
+           (error 'open-output-file "not a string" filename))]
       [(filename options)
        (if (string? filename)
            ($open-output-file filename options)
-           (error 'open-output-file "~s is not a string" filename))]))
+           (error 'open-output-file "not a string" filename))]))
 
   (define with-output-to-file
      (lambda (name proc . args)
        (unless (string? name) 
-         (error 'with-output-to-file "~s is not a string" name))
+         (error 'with-output-to-file "not a string" name))
        (unless (procedure? proc)
-         (error 'with-output-to-file "~s is not a procedure" proc))
+         (error 'with-output-to-file "not a procedure" proc))
        (let ([p (apply open-output-file name args)]
              [shot #f])
          (call-with-values 
@@ -199,9 +190,9 @@
   (define call-with-output-file
      (lambda (name proc . args)
        (unless (string? name) 
-         (error 'call-with-output-file "~s is not a string" name))
+         (error 'call-with-output-file "not a string" name))
        (unless (procedure? proc)
-         (error 'call-with-output-file "~s is not a procedure" proc))
+         (error 'call-with-output-file "not a procedure" proc))
        (let ([p (apply open-output-file name args)])
          (call-with-values (lambda () (proc p))
             (case-lambda
diff --git a/scheme/ikarus.io.output-strings.ss b/scheme/ikarus.io.output-strings.ss
index 57c381c..a174ecd 100644
--- a/scheme/ikarus.io.output-strings.ss
+++ b/scheme/ikarus.io.output-strings.ss
@@ -24,12 +24,12 @@
              [(__ y () body)
               (if (null? y) 
                   body
-                  (error 'message-case "unmatched ~s" (cons tmsg targs)))]
+                  (error 'message-case "unmatched" (cons tmsg targs)))]
              [(__ y (a a* (... ...)) body)
               (if (pair? y)
                   (let ([a (car y)] [d (cdr y)])
                     (match-and-bind d (a* (... ...)) body))
-                  (error 'message-case "unmatched ~s" (cons tmsg targs)))]))
+                  (error 'message-case "unmatched" (cons tmsg targs)))]))
          (case tmsg
            [(msg-name) 
             (match-and-bind targs (msg-arg* ...) (begin b b* ...))] ...
@@ -120,18 +120,19 @@
                                (set! buffer-list (cons (bv-copy buff) buffer-list))
                                ($bytevector-set! buff 0 b)
                                ($set-port-index! p 1))
-                             (error 'write-byte "port ~s is closed" p))))
-                     (error 'write-byte "~s is not an output-port" p))
-                 (error 'write-byte "~s is not a byte" b))]
+                             (error 'write-byte "port is closed" p))))
+                     (error 'write-byte "not an output-port" p))
+                 (error 'write-byte "not a byte" b))]
             [(write-char c p)
              (if (char? c)
                  (if (output-port? p)
                      (let ([b ($char->fixnum c)])
                        (if ($fx<= b 127)
                            ($write-byte b p)
-                           (error 'write-char "multibyte write of ~s is not implemented" c)))
-                     (error 'write-char "~s is not an output-port" p))
-                 (error 'write-char "~s is not a character" c))]
+                           (error 'write-char 
+                             "BUG: multibyte write of is not implemented" c)))
+                     (error 'write-char "not an output-port" p))
+                 (error 'write-char "not a character" c))]
             [(flush-output-port p)
              (void)]
             [(close-port p)
@@ -143,8 +144,8 @@
                  ($port-buffer p) 
                  ($port-index p)
                  buffer-list))]
-            [else (error 'output-handler 
-                         "unhandled message ~s" (cons msg args))])))
+            [else 
+             (error 'output-handler "unhandled message" (cons msg args))])))
       output-handler))
 
   (define open-output-string 
@@ -157,12 +158,12 @@
     (lambda (p)
       (if (output-port? p)
           (($port-handler p) 'get-output-string p)
-          (error 'get-output-string "~s is not an output port" p))))
+          (error 'get-output-string "not an output port" p))))
   
   (define with-output-to-string
     (lambda (f)
       (unless (procedure? f)
-        (error 'with-output-to-string "~s is not a procedure" f))
+        (error 'with-output-to-string "not a procedure" f))
       (let ([p (open-output-string)])
         (parameterize ([current-output-port p]) (f))
         (get-output-string p))))
diff --git a/scheme/ikarus.lists.ss b/scheme/ikarus.lists.ss
index d26a3ad..8e133c5 100644
--- a/scheme/ikarus.lists.ss
+++ b/scheme/ikarus.lists.ss
@@ -55,11 +55,11 @@
         [(n)
          (if (and (fixnum? n) ($fx>= n 0))
              (f n (void) '())
-             (error 'make-list "~s is not a valid length" n))]
+             (error 'make-list "not a valid length" n))]
         [(n fill)
          (if (and (fixnum? n) ($fx>= n 0))
              (f n fill '())
-             (error 'make-list "~s is not a valid length" n))])))
+             (error 'make-list "not a valid length" n))])))
 
 
   (define length
@@ -70,13 +70,13 @@
                       (if (pair? h)
                           (if (not (eq? h t))
                               (race ($cdr h) ($cdr t) ls ($fx+ n 2))
-                              (error 'length "circular list ~s" ls))
+                              (error 'length "circular list" ls))
                           (if (null? h)
                               ($fx+ n 1)
-                              (error 'length "~s is not a proper list" ls))))
+                              (error 'length "not a proper list" ls))))
                    (if (null? h)
                        n
-                       (error 'length "~s is not a proper list" ls))))])
+                       (error 'length "not a proper list" ls))))])
        (lambda (ls)
          (race ls ls ls 0))))
 
@@ -88,14 +88,14 @@
             [($fxzero? i) 
              (if (pair? ls)
                  ($car ls)
-                 (error 'list-ref "index ~s is out of range for ~s" index list))]
+                 (error 'list-ref "index is out of range" index list))]
             [(pair? ls)
              (f ($cdr ls) ($fxsub1 i))]
             [(null? ls) 
-             (error 'list-rec "index ~s is out of range for ~s" index list)]
-            [else (error 'list-ref "~s is not a list" list)])))
+             (error 'list-rec "index is out of range" index list)]
+            [else (error 'list-ref "not a list" list)])))
       (unless (and (fixnum? index) ($fx>= index 0))
-        (error 'list-ref "~s is not a valid index" index))
+        (error 'list-ref "not a valid index" index))
       (f list index)))
 
 
@@ -108,10 +108,10 @@
             [(pair? ls)
              (f ($cdr ls) ($fxsub1 i))]
             [(null? ls) 
-             (error 'list-tail "index ~s is out of range for ~s" index list)]
-            [else (error 'list-tail "~s is not a list" list)])))
+             (error 'list-tail "index is out of range" index list)]
+            [else (error 'list-tail "not a list" list)])))
       (unless (and (fixnum? index) ($fx>= index 0))
-        (error 'list-tail "~s is not a valid index" index))
+        (error 'list-tail "not a valid index" index))
       (f list index)))
 
   (module (append)
@@ -123,13 +123,13 @@
                    (if (not (eq? h t))
                        (let ([a2 ($car h)])
                          (reverse ($cdr h) ($cdr t) ls (cons a2 (cons a1 ac))))
-                       (error 'append "circular list ~s" ls))
+                       (error 'append "circular list" ls))
                    (if (null? h)
                        (cons a1 ac)
-                       (error 'append "~s is not a proper list" ls))))
+                       (error 'append "not a proper list" ls))))
             (if (null? h)
                 ac 
-                (error 'append "~s is not a proper list" ls)))))
+                (error 'append "not a proper list" ls)))))
     (define revcons
       (lambda (ls ac)
         (cond
@@ -158,13 +158,13 @@
                       (if (pair? h)
                           (if (not (eq? h t))
                               (race ($cdr h) ($cdr t) ls (cons ($car h) ac))
-                              (error 'reverse "~s is a circular list" ls))
+                              (error 'reverse "circular list" ls))
                           (if (null? h)
                               ac
-                              (error 'reverse "~s is not a proper list" ls))))
+                              (error 'reverse "not a proper list" ls))))
                    (if (null? h)
                        ac
-                       (error 'reverse "~s is not a proper list" ls))))])
+                       (error 'reverse "not a proper list" ls))))])
        (lambda (x)
          (race x x x '()))))
   
@@ -176,14 +176,14 @@
                        (if (pair? h)
                            (if (not (eq? h t))
                                (race ($cdr h) ($cdr t) ls h)
-                               (error 'last-pair "~s is a circular list" ls))
+                               (error 'last-pair "circular list" ls))
                            last))
                     last))])
        (lambda (x)
          (if (pair? x)
              (let ([d (cdr x)])
                (race d d x x))
-             (error 'last-pair "~s is not a pair" x)))))
+             (error 'last-pair "not a pair" x)))))
 
   (define memq
     (letrec ([race
@@ -197,13 +197,13 @@
                                    h
                                    (if (not (eq? h t))
                                        (race ($cdr h) ($cdr t) ls x)
-                                       (error 'memq "circular list ~s" ls)))
+                                       (error 'memq "circular list" ls)))
                                (if (null? h)
                                    '#f
-                                   (error 'memq "~s is not a proper list" ls)))))
+                                   (error 'memq "not a proper list" ls)))))
                      (if (null? h)
                          '#f
-                         (error 'memq "~s is not a proper list" ls))))])
+                         (error 'memq "not a proper list" ls))))])
        (lambda (x ls)
          (race ls ls ls x))))
 
@@ -219,13 +219,13 @@
                                    h
                                    (if (not (eq? h t))
                                        (race ($cdr h) ($cdr t) ls x)
-                                       (error 'memv "circular list ~s" ls)))
+                                       (error 'memv "circular list" ls)))
                                (if (null? h)
                                    '#f
-                                   (error 'memv "~s is not a proper list" ls)))))
+                                   (error 'memv "not a proper list" ls)))))
                      (if (null? h)
                          '#f
-                         (error 'memv "~s is not a proper list" ls))))])
+                         (error 'memv "not a proper list" ls))))])
        (lambda (x ls)
          (race ls ls ls x))))
   
@@ -241,13 +241,13 @@
                                    h
                                    (if (not (eq? h t))
                                        (race ($cdr h) ($cdr t) ls x)
-                                       (error 'member "circular list ~s" ls)))
+                                       (error 'member "circular list" ls)))
                                (if (null? h)
                                    '#f
-                                   (error 'member "~s is not a proper list" ls)))))
+                                   (error 'member "not a proper list" ls)))))
                      (if (null? h)
                          '#f
-                         (error 'member "~s is not a proper list" ls))))])
+                         (error 'member "not a proper list" ls))))])
        (lambda (x ls)
          (race ls ls ls x))))
 
@@ -264,16 +264,16 @@
                                    h
                                    (if (not (eq? h t))
                                        (race ($cdr h) ($cdr t) ls p)
-                                       (error 'memp "circular list ~s" ls)))
+                                       (error 'memp "circular list" ls)))
                                (if (null? h)
                                    '#f
-                                   (error 'memp "~s is not a proper list" ls)))))
+                                   (error 'memp "not a proper list" ls)))))
                      (if (null? h)
                          '#f
-                         (error 'memp "~s is not a proper list" ls))))])
+                         (error 'memp "not a proper list" ls))))])
        (lambda (p ls)
          (unless (procedure? p)
-           (error 'memp "~s is not a procedure" p))
+           (error 'memp "not a procedure" p))
          (race ls ls ls p))))
 
   (define find
@@ -290,16 +290,16 @@
                                        a
                                        (if (not (eq? h t))
                                            (race ($cdr h) ($cdr t) ls p)
-                                           (error 'find "circular list ~s" ls))))
+                                           (error 'find "circular list" ls))))
                                  (if (null? h)
                                      '#f
-                                     (error 'find "~s is not a proper list" ls))))))
+                                     (error 'find "not a proper list" ls))))))
                      (if (null? h)
                          '#f
-                         (error 'find "~s is not a proper list" ls))))])
+                         (error 'find "not a proper list" ls))))])
        (lambda (p ls)
          (unless (procedure? p)
-           (error 'find "~s is not a procedure" p))
+           (error 'find "not a procedure" p))
          (race ls ls ls p))))
 
   (define assq
@@ -317,16 +317,16 @@
                                               (if (eq? ($car a) x)
                                                   a
                                                   (race x ($cdr h) ($cdr t) ls))
-                                              (error 'assq "malformed alist ~s"
+                                              (error 'assq "malformed alist"
                                                      ls)))
-                                       (error 'assq "circular list ~s" ls))
+                                       (error 'assq "circular list" ls))
                                    (if (null? h)
                                        #f
-                                       (error 'assq "~s is not a proper list" ls))))
-                           (error 'assq "malformed alist ~s" ls)))
+                                       (error 'assq "not a proper list" ls))))
+                           (error 'assq "malformed alist" ls)))
                     (if (null? h)
                         #f
-                        (error 'assq "~s is not a proper list" ls))))])
+                        (error 'assq "not a proper list" ls))))])
        (lambda (x ls) 
          (race x ls ls ls))))
 
@@ -346,19 +346,19 @@
                                               (if (p ($car a))
                                                   a
                                                   (race p ($cdr h) ($cdr t) ls))
-                                              (error 'assp "malformed alist ~s"
+                                              (error 'assp "malformed alist"
                                                      ls)))
-                                       (error 'assp "circular list ~s" ls))
+                                       (error 'assp "circular list" ls))
                                    (if (null? h)
                                        #f
-                                       (error 'assp "~s is not a proper list" ls))))
-                           (error 'assp "malformed alist ~s" ls)))
+                                       (error 'assp "not a proper list" ls))))
+                           (error 'assp "malformed alist" ls)))
                     (if (null? h)
                         #f
-                        (error 'assp "~s is not a proper list" ls))))])
+                        (error 'assp "not a proper list" ls))))])
        (lambda (p ls)
          (unless (procedure? p) 
-           (error 'assp "~s is not a procedure" p))
+           (error 'assp "not a procedure" p))
          (race p ls ls ls))))
 
   (define assv
@@ -376,16 +376,16 @@
                                               (if (eqv? ($car a) x)
                                                   a
                                                   (race x ($cdr h) ($cdr t) ls))
-                                              (error 'assv "malformed alist ~s"
+                                              (error 'assv "malformed alist"
                                                      ls)))
-                                       (error 'assv "circular list ~s" ls))
+                                       (error 'assv "circular list" ls))
                                    (if (null? h)
                                        #f
-                                       (error 'assv "~s is not a proper list" ls))))
-                           (error 'assv "malformed alist ~s" ls)))
+                                       (error 'assv "not a proper list" ls))))
+                           (error 'assv "malformed alist" ls)))
                     (if (null? h)
                         #f
-                        (error 'assv "~s is not a proper list" ls))))])
+                        (error 'assv "not a proper list" ls))))])
        (lambda (x ls) 
          (race x ls ls ls))))
 
@@ -404,16 +404,16 @@
                                               (if (equal? ($car a) x)
                                                   a
                                                   (race x ($cdr h) ($cdr t) ls))
-                                              (error 'assoc "malformed alist ~s"
+                                              (error 'assoc "malformed alist"
                                                      ls)))
-                                       (error 'assoc "circular list ~s" ls))
+                                       (error 'assoc "circular list" ls))
                                    (if (null? h)
                                        #f
-                                       (error 'assoc "~s is not a proper list" ls))))
-                           (error 'assoc "malformed alist ~s" ls)))
+                                       (error 'assoc "not a proper list" ls))))
+                           (error 'assoc "malformed alist" ls)))
                     (if (null? h)
                         #f
-                        (error 'assoc "~s is not a proper list" ls))))])
+                        (error 'assoc "not a proper list" ls))))])
        (lambda (x ls) 
          (race x ls ls ls))))
 
@@ -433,23 +433,23 @@
                                           (if (cmp ($car h) x)
                                               (race ($cdr h) ($cdr t) ls x)
                                               (cons ($car h) (race ($cdr h) ($cdr t) ls x)))
-                                          (error 'name "circular list ~s" ls))
+                                          (error 'name "circular list" ls))
                                       (if (null? h)
                                           '()
-                                          (error 'name "~s is not a proper list" ls))))
+                                          (error 'name "not a proper list" ls))))
                                 (let ([a0 ($car h)] [h ($cdr h)])
                                   (if (pair? h)
                                       (if (not (eq? h t))
                                           (if (cmp ($car h) x)
                                               (cons a0 (race ($cdr h) ($cdr t) ls x))
                                               (cons* a0 ($car h) (race ($cdr h) ($cdr t) ls x)))
-                                          (error 'name "circular list ~s" ls))
+                                          (error 'name "circular list" ls))
                                       (if (null? h)
                                           (list a0)
-                                          (error 'name "~s is not a proper list" ls)))))
+                                          (error 'name "not a proper list" ls)))))
                             (if (null? h)
                                 '()
-                                (error 'name "~s is not a proper list" ls))))])
+                                (error 'name "not a proper list" ls))))])
               (lambda (x ls)
                 (check x ls)
                 (race ls ls ls x))))]))
@@ -459,11 +459,11 @@
     (define-remover remp (lambda (elt p) (p elt))
       (lambda (x ls) 
         (unless (procedure? x)
-          (error 'remp "~s is not a procedure" x)))) 
+          (error 'remp "not a procedure" x)))) 
     (define-remover filter (lambda (elt p) (not (p elt)))
       (lambda (x ls) 
         (unless (procedure? x)
-          (error 'filter "~s is not a procedure" x)))))
+          (error 'filter "not a procedure" x)))))
 
 
   (module (map)
@@ -558,7 +558,7 @@
        (case-lambda
          [(f ls) 
           (unless (procedure? f)
-            (error who "~s is not a procedure" f))
+            (error who "not a procedure" f))
           (cond
             [(pair? ls)
              (let ([d ($cdr ls)])
@@ -567,7 +567,7 @@
             [else (error who "improper list")])]
          [(f ls ls2)
           (unless (procedure? f)
-            (error who "~s is not a procedure" f))
+            (error who "not a procedure" f))
           (cond
             [(pair? ls)
              (if (pair? ls2)
@@ -581,7 +581,7 @@
             [else (error who "not a list")])]
          [(f ls . ls*)
           (unless (procedure? f)
-            (error who "~s is not a procedure" f))
+            (error who "not a procedure" f))
           (cond
             [(pair? ls)
              (let ([n (len ls ls 0)])
@@ -648,7 +648,7 @@
        (case-lambda
          [(f ls)
           (unless (procedure? f)
-            (error who "~s is not a procedure" f))
+            (error who "not a procedure" f))
           (cond
             [(pair? ls)
              (let ([d ($cdr ls)])
@@ -657,7 +657,7 @@
             [else (error who "improper list")])]
          [(f ls ls2)
           (unless (procedure? f)
-            (error who "~s is not a procedure" f))
+            (error who "not a procedure" f))
           (cond
             [(pair? ls)
              (if (pair? ls2)
@@ -672,23 +672,23 @@
             [else (error who "not a list")])]
          [(f ls . ls*)
           (unless (procedure? f) 
-            (error 'for-each "~s is not a procedure" f))
+            (error 'for-each "not a procedure" f))
           (unless (list? ls) 
-            (error 'for-each "~s is not a list" ls))
+            (error 'for-each "not a list" ls))
           (let ([n (length ls)])
             (for-each 
               (lambda (x) 
                 (unless (and (list? x) (= (length x) n))
-                  (error 'for-each "~s is not a list" x)))
+                  (error 'for-each "not a list" x)))
               ls*)
             (let loop ([n (length ls)] [ls ls] [ls* ls*])
               (cond
                 [($fx= n 0) 
                  (unless (and (null? ls) (andmap null? ls*))
-                   (error 'for-each "list modified by ~s" f))]
+                   (error 'for-each "list modified" f))]
                 [else
                  (unless (and (pair? ls) (andmap pair? ls*))
-                   (error 'for-each "list modified by ~s" f))
+                   (error 'for-each "list modified" f))
                  (apply f (car ls) (map car ls*))
                  (loop (fx- n 1) (cdr ls) (map cdr ls*))])))])))
 
@@ -748,7 +748,7 @@
        (case-lambda
          [(f ls)
           (unless (procedure? f)
-            (error who "~s is not a procedure" f))
+            (error who "not a procedure" f))
           (cond
             [(pair? ls)
              (let ([d ($cdr ls)])
@@ -757,7 +757,7 @@
             [else (error who "improper list")])]
          [(f ls ls2)
           (unless (procedure? f)
-            (error who "~s is not a procedure" f))
+            (error who "not a procedure" f))
           (cond
             [(pair? ls)
              (if (pair? ls2)
@@ -772,7 +772,7 @@
             [else (error who "not a list")])]
          [(f ls . ls*)
           (unless (procedure? f) 
-            (error who "~s is not a procedure" f))
+            (error who "not a procedure" f))
           (error who "vararg not yet supported")])))
 
 
@@ -811,7 +811,7 @@
        (case-lambda
          [(f ls)
           (unless (procedure? f)
-            (error who "~s is not a procedure" f))
+            (error who "not a procedure" f))
           (cond
             [(pair? ls)
              (let ([d ($cdr ls)])
@@ -829,7 +829,7 @@
                      (let ([a0 ($car h)] [h ($cdr h)])
                         (if (pair? h)
                             (if (eq? h t)
-                                (error 'partition "circular list ~s" ls)
+                                (error 'partition "circular list" ls)
                                 (let ([a1 ($car h)])
                                   (let-values ([(a* b*) (race ($cdr h) ($cdr t) ls p)])
                                     (if (p a0) 
@@ -843,13 +843,13 @@
                                 (if (p a0)
                                     (values (list a0) '())
                                     (values '() (list a0)))
-                                (error 'parititon "~s is not a proper list" ls))))
+                                (error 'parititon "not a proper list" ls))))
                      (if (null? h)
                          (values '() '())
-                         (error 'parition "~s is not a proper list" ls))))])
+                         (error 'parition "not a proper list" ls))))])
        (lambda (p ls)
          (unless (procedure? p) 
-           (error 'partition "~s is not a procedure" p))
+           (error 'partition "not a procedure" p))
          (race ls ls ls p))))
 
 
@@ -866,7 +866,7 @@
                (error who "length mismatch")
                (if (list? (car ls*))
                    (err* (cdr ls*))
-                   (error who "~s is not a proper list" (car ls*)))))
+                   (error who "not a proper list" (car ls*)))))
          (define (cars+cdrs ls ls*)
            (cond
              [(null? ls) (values '() '())]
@@ -877,22 +877,22 @@
                       (values (cons (car a) cars) (cons (cdr a) cdrs)))
                     (if (list? (car ls*)) 
                         (error who "length mismatch")
-                        (error who "~s is not a proper list" (car ls*)))))]))
+                        (error who "not a proper list" (car ls*)))))]))
          (define (loop1 f a h t ls)
            (if (pair? h)
                (let ([b (car h)] [h (cdr h)])
                  (combine (f a)
                    (if (pair? h)
                        (if (eq? h t)
-                           (error who "~s is circular" ls)
+                           (error who "circular" ls)
                            (let ([c (car h)] [h (cdr h)])
                              (combine (f b) (loop1 f c h (cdr t) ls))))
                        (if (null? h) 
                            (f b)
-                           (combine (f b) (error who "~s is not a proper list" ls))))))
+                           (combine (f b) (error who "not a proper list" ls))))))
                (if (null? h)
                    (f a)
-                   (combine (f a) (error who "~s is not a proper list" ls)))))
+                   (combine (f a) (error who "not a proper list" ls)))))
          (define (loopn f a a* h h* t ls ls*)
            (if (pair? h)
                (let-values ([(b* h*) (cars+cdrs h* ls*)])
@@ -900,7 +900,7 @@
                    (combine (apply f a a*)
                      (if (pair? h)
                          (if (eq? h t)
-                             (error who "~s is circular" ls)
+                             (error who "circular" ls)
                              (let-values ([(c* h*) (cars+cdrs h* ls*)])
                                (let ([c (car h)] [h (cdr h)])
                                  (combine (apply f b b*) 
@@ -915,15 +915,15 @@
            (case-lambda
              [(f ls)
               (unless (procedure? f) 
-                (error who "~s is not a procedure" f))
+                (error who "not a procedure" f))
               (if (pair? ls)
                   (loop1 f (car ls) (cdr ls) (cdr ls) ls)
                   (if (null? ls)
                       (combine)
-                      (error who "~s is not a list" ls)))]
+                      (error who "not a list" ls)))]
              [(f ls . ls*)
               (unless (procedure? f) 
-                (error who "~s is not a procedure" f))
+                (error who "not a procedure" f))
               (if (pair? ls)
                   (let-values ([(cars cdrs) (cars+cdrs ls* ls*)])
                     (loopn f (car ls) cars (cdr ls) cdrs (cdr ls) ls ls*))
@@ -943,7 +943,7 @@
           (error who "length mismatch")
           (if (list? (car ls*))
               (err* (cdr ls*))
-              (error who "~s is not a proper list" (car ls*)))))
+              (error who "not a proper list" (car ls*)))))
     (define (cars+cdrs ls ls*)
       (cond
         [(null? ls) (values '() '())]
@@ -954,28 +954,28 @@
                  (values (cons (car a) cars) (cons (cdr a) cdrs)))
                (if (list? (car ls*)) 
                    (error who "length mismatch")
-                   (error who "~s is not a proper list" (car ls*)))))]))
+                   (error who "not a proper list" (car ls*)))))]))
      (define (loop1 f nil h t ls)
        (if (pair? h)
            (let ([a (car h)] [h (cdr h)])
              (if (pair? h) 
                  (if (eq? h t)
-                     (error who "~s is circular" ls)
+                     (error who "circular" ls)
                      (let ([b (car h)] [h (cdr h)] [t (cdr t)])
                        (loop1 f (f (f nil a) b) h t ls)))
                  (if (null? h)
                      (f nil a)
-                     (error who "~s is not a proper list" ls))))
+                     (error who "not a proper list" ls))))
            (if (null? h)
                nil
-               (error who "~s is not a proper list" ls))))
+               (error who "not a proper list" ls))))
     (define (loopn f nil h h* t ls ls*)
       (if (pair? h)
           (let-values ([(a* h*) (cars+cdrs h* ls*)])
             (let ([a (car h)] [h (cdr h)])
               (if (pair? h) 
                   (if (eq? h t)
-                      (error who "~s is circular" ls)
+                      (error who "circular" ls)
                       (let-values ([(b* h*) (cars+cdrs h* ls*)])
                         (let ([b (car h)] [h (cdr h)] [t (cdr t)])
                           (loopn f 
@@ -991,11 +991,11 @@
       (case-lambda
         [(f nil ls) 
          (unless (procedure? f)
-           (error who "~s is not a procedure" f))
+           (error who "not a procedure" f))
          (loop1 f nil ls ls ls)]
         [(f nil ls . ls*) 
          (unless (procedure? f)
-           (error who "~s is not a procedure" f))
+           (error who "not a procedure" f))
          (loopn f nil ls ls* ls ls ls*)])))
   
   (module (fold-right)
@@ -1007,7 +1007,7 @@
           (error who "length mismatch")
           (if (list? (car ls*))
               (err* (cdr ls*))
-              (error who "~s is not a proper list" (car ls*)))))
+              (error who "not a proper list" (car ls*)))))
     (define (cars+cdrs ls ls*)
       (cond
         [(null? ls) (values '() '())]
@@ -1018,28 +1018,28 @@
                  (values (cons (car a) cars) (cons (cdr a) cdrs)))
                (if (list? (car ls*)) 
                    (error who "length mismatch")
-                   (error who "~s is not a proper list" (car ls*)))))]))
+                   (error who "not a proper list" (car ls*)))))]))
      (define (loop1 f nil h t ls)
        (if (pair? h)
            (let ([a (car h)] [h (cdr h)])
              (if (pair? h) 
                  (if (eq? h t)
-                     (error who "~s is circular" ls)
+                     (error who "circular" ls)
                      (let ([b (car h)] [h (cdr h)] [t (cdr t)])
                        (f a (f b (loop1 f nil h t ls)))))
                  (if (null? h)
                      (f a nil)
-                     (error who "~s is not a proper list" ls))))
+                     (error who "not a proper list" ls))))
            (if (null? h)
                nil
-               (error who "~s is not a proper list" ls))))
+               (error who "not a proper list" ls))))
     (define (loopn f nil h h* t ls ls*)
       (if (pair? h)
           (let-values ([(a* h*) (cars+cdrs h* ls*)])
             (let ([a (car h)] [h (cdr h)])
               (if (pair? h) 
                   (if (eq? h t)
-                      (error who "~s is circular" ls)
+                      (error who "circular" ls)
                       (let-values ([(b* h*) (cars+cdrs h* ls*)])
                         (let ([b (car h)] [h (cdr h)] [t (cdr t)])
                           (apply f a
@@ -1058,11 +1058,11 @@
       (case-lambda
         [(f nil ls) 
          (unless (procedure? f)
-           (error who "~s is not a procedure" f))
+           (error who "not a procedure" f))
          (loop1 f nil ls ls ls)]
         [(f nil ls . ls*) 
          (unless (procedure? f)
-           (error who "~s is not a procedure" f))
+           (error who "not a procedure" f))
          (loopn f nil ls ls* ls ls ls*)]
         )))
 
diff --git a/scheme/ikarus.load.ss b/scheme/ikarus.load.ss
index e164131..d661df7 100644
--- a/scheme/ikarus.load.ss
+++ b/scheme/ikarus.load.ss
@@ -20,9 +20,9 @@
       [(x) (load x load-handler)]
       [(x eval-proc)
        (unless (string? x)
-         (error 'load "~s is not a string" x))
+         (error 'load "not a string" x))
        (unless (procedure? eval-proc)
-         (error 'load "~s is not a procedure" eval-proc))
+         (error 'load "not a procedure" eval-proc))
        (let ([p (open-input-file x)])
          (let ([x (read-initial p)])
            (unless (eof-object? x)
diff --git a/scheme/ikarus.numerics.ss b/scheme/ikarus.numerics.ss
index bef83ee..f2b982d 100644
--- a/scheme/ikarus.numerics.ss
+++ b/scheme/ikarus.numerics.ss
@@ -28,7 +28,7 @@
   
   (define (flonum-bytes f)
     (unless (flonum? f) 
-      (error 'flonum-bytes "~s is not a flonum" f))
+      (error 'flonum-bytes "not a flonum" f))
     (values 
       ($flonum-u8-ref f 0)
       ($flonum-u8-ref f 1)
@@ -40,7 +40,7 @@
       ($flonum-u8-ref f 7)))
   (define (flonum-parts x)
     (unless (flonum? x) 
-      (error 'flonum-parts "~s is not a flonum" x))
+      (error 'flonum-parts "not a flonum" x))
     (let-values ([(b0 b1 b2 b3 b4 b5 b6 b7) (flonum-bytes x)])
       (values 
         (zero? (fxlogand b0 128)) 
@@ -95,7 +95,7 @@
 
   (define (flnumerator x) 
     (unless (flonum? x) 
-      (error 'flnumerator "~s is not a flonum" x))
+      (error 'flnumerator "not a flonum" x))
     (cond
       [($flonum-integer? x) x]
       [($flonum-rational? x) 
@@ -104,7 +104,7 @@
 
   (define (fldenominator x) 
     (unless (flonum? x) 
-      (error 'fldenominator "~s is not a flonum" x))
+      (error 'fldenominator "not a flonum" x))
     (cond
       [($flonum-integer? x) 1.0]
       [($flonum-rational? x) 
@@ -114,48 +114,48 @@
 
   (define (fleven? x)
     (unless (flonum? x) 
-      (error 'fleven? "~s is not a flonum" x))
+      (error 'fleven? "not a flonum" x))
     (let ([v ($flonum->exact x)])
       (cond
         [(fixnum? v) ($fx= ($fxlogand v 1) 0)]
         [(bignum? v) 
          (foreign-call "ikrt_even_bn" v)]
-        [else (error 'fleven? "~s is not an integer flonum" x)])))
+        [else (error 'fleven? "not an integer flonum" x)])))
 
   (define (flodd? x)
     (unless (flonum? x) 
-      (error 'flodd? "~s is not a flonum" x))
+      (error 'flodd? "not a flonum" x))
     (let ([v ($flonum->exact x)])
       (cond
         [(fixnum? v) ($fx= ($fxlogand v 1) 1)]
         [(bignum? v) 
          (not (foreign-call "ikrt_even_bn" v))]
-        [else (error 'flodd? "~s is not an integer flonum" x)])))
+        [else (error 'flodd? "not an integer flonum" x)])))
 
   (define (flinteger? x)
     (if (flonum? x)
         ($flonum-integer? x)
-        (error 'flinteger? "~s is not a flonum" x)))
+        (error 'flinteger? "not a flonum" x)))
 
   (define (flinfinite? x) 
     (if (flonum? x) 
         (let ([be (fxlogand ($flonum-signed-biased-exponent x) (sub1 (fxsll 1 11)))])
           (and (fx= be 2047)  ;;; nans and infs
                ($zero-m? x)))
-        (error 'flinfinite? "~s is not a flonum" x)))
+        (error 'flinfinite? "not a flonum" x)))
 
   (define (flnan? x) 
     (if (flonum? x) 
         (let ([be (fxlogand ($flonum-signed-biased-exponent x) (sub1 (fxsll 1 11)))])
           (and (fx= be 2047)  ;;; nans and infs
                (not ($zero-m? x))))
-        (error 'flnan? "~s is not a flonum" x)))
+        (error 'flnan? "not a flonum" x)))
 
   (define (flfinite? x) 
     (if (flonum? x) 
         (let ([be (fxlogand ($flonum-signed-biased-exponent x) (sub1 (fxsll 1 11)))])
           (not (fx= be 2047)))
-        (error 'flfinite? "~s is not a flonum" x)))
+        (error 'flfinite? "not a flonum" x)))
   
   (define ($flzero? x)
     (let ([be (fxlogand ($flonum-signed-biased-exponent x) (sub1 (fxsll 1 11)))])
@@ -189,67 +189,67 @@
     (cond
       [(flonum? x)
        (or ($flonum->exact x)
-           (error 'inexact->exact "~s has no real value" x))]
+           (error 'inexact->exact "no real value" x))]
       [(or (fixnum? x) (ratnum? x) (bignum? x)) x]
       [else
-       (error 'inexact->exact "~s is not an inexact number" x)]))
+       (error 'inexact->exact "not an inexact number" x)]))
 
   (define (exact x)
     (cond
       [(flonum? x)
        (or ($flonum->exact x)
-           (error 'exact "~s has no real value" x))]
+           (error 'exact "no real value" x))]
       [(or (fixnum? x) (ratnum? x) (bignum? x)) x]
       [else
-       (error 'exact "~s is not an inexact number" x)]))
+       (error 'exact "not an inexact number" x)]))
 
 
   (define (flpositive? x)
     (if (flonum? x) 
         ($fl> x 0.0)
-        (error 'flpositive? "~s is not a flonum" x)))
+        (error 'flpositive? "not a flonum" x)))
   
   (define (flabs x)
     (if (flonum? x) 
         (if ($fl> x 0.0) 
             ($fl* x -1.0)
             x)
-        (error 'flabs "~s is not a flonum" x)))
+        (error 'flabs "not a flonum" x)))
 
   (define (fixnum->flonum x)
     (if (fixnum? x) 
         ($fixnum->flonum x)
-        (error 'fixnum->flonum "~s is not a fixnum")))
+        (error 'fixnum->flonum "not a fixnum")))
 
   (define (flsin x)
     (if (flonum? x) 
         (foreign-call "ikrt_fl_sin" x)
-        (error 'flsin "~s is not a flonum" x)))
+        (error 'flsin "not a flonum" x)))
 
   (define (flcos x)
     (if (flonum? x) 
         (foreign-call "ikrt_fl_cos" x)
-        (error 'flcos "~s is not a flonum" x)))
+        (error 'flcos "not a flonum" x)))
 
   (define (fltan x)
     (if (flonum? x) 
         (foreign-call "ikrt_fl_tan" x)
-        (error 'fltan "~s is not a flonum" x)))
+        (error 'fltan "not a flonum" x)))
 
   (define (flasin x)
     (if (flonum? x) 
         (foreign-call "ikrt_fl_asin" x)
-        (error 'flasin "~s is not a flonum" x)))
+        (error 'flasin "not a flonum" x)))
 
   (define (flacos x)
     (if (flonum? x) 
         (foreign-call "ikrt_fl_acos" x)
-        (error 'flacos "~s is not a flonum" x)))
+        (error 'flacos "not a flonum" x)))
 
   (define (flatan x)
     (if (flonum? x) 
         (foreign-call "ikrt_fl_atan" x)
-        (error 'flatan "~s is not a flonum" x)))
+        (error 'flatan "not a flonum" x)))
 
 
   (define (flfloor x)
@@ -264,7 +264,7 @@
            [(ratnum? e)
             (exact->inexact (ratnum-floor e))] 
            [else x]))]
-      [else (error 'flfloor "~s is not a flonum" x)]))
+      [else (error 'flfloor "not a flonum" x)]))
 
   (define (flceiling x)
     (cond
@@ -274,19 +274,19 @@
            [(ratnum? e)
             (exact->inexact (ceiling e))] 
            [else x]))]
-      [else (error 'flceiling "~s is not a flonum" x)]))
+      [else (error 'flceiling "not a flonum" x)]))
 
   (define (flexp x)
     (if (flonum? x) 
         (foreign-call "ikrt_fl_exp" x ($make-flonum))
-        (error 'flexp "~s is not a flonum" x)))
+        (error 'flexp "not a flonum" x)))
 
   (define (fllog x)
     (if (flonum? x)
         (if ($fl>= x 0.0) 
             (foreign-call "ikrt_fl_log" x)
-            (error 'fllog "argument ~s should not be negative" x))
-        (error 'fllog "~s is not a flonum" x)))
+            (error 'fllog "argument should not be negative" x))
+        (error 'fllog "not a flonum" x)))
 
   (define (flexpt x y)
     (if (flonum? x)
@@ -297,8 +297,8 @@
                 [(bignum? y^) (inexact (expt x y^))]
                 [else
                  (foreign-call "ikrt_flfl_expt" x y ($make-flonum))]))
-            (error 'flexpt "~s is not a flonum" y))
-        (error 'fllog "~s is not a flonum" x)))
+            (error 'flexpt "not a flonum" y))
+        (error 'fllog "not a flonum" x)))
 
 
   )
@@ -477,7 +477,7 @@
             (fxlogor (fxsll b2 4) (fxsra b1 4))
             (fxlogor (fxsll b1 4) (fxsra b0 4))
             (fxsra b0 3))]
-        [else (error '$float/aux "invalid b7=~s" b7)]))
+        [else (error '$float/aux "BUG: invalid b7" b7)]))
     (define (bignum->flonum x)
       (define (bignum/4->flonum x) 
         ($flonum/aux ($bignum-positive? x) -24 
@@ -533,7 +533,7 @@
               (aux x bn bytes))))
               
       (unless (bignum? x)
-        (error 'bignum->flonum "~s is not a bignum" x))
+        (error 'bignum->flonum "not a bignum" x))
       (let ([bytes ($bignum-size x)])
         (case bytes
           [(4)  (bignum/4->flonum x)]
@@ -565,7 +565,7 @@
               (+ (* x ($ratnum-d y)) ($ratnum-n y))
               ($ratnum-d y))]
            [else 
-            (error '+ "~s is not a number" y)])]
+            (error '+ "not a number" y)])]
         [(bignum? x)
          (cond
            [(fixnum? y)
@@ -579,7 +579,7 @@
               (+ (* x ($ratnum-d y)) ($ratnum-n y))
               ($ratnum-d y))] 
            [else 
-            (error '+ "~s is not a number" y)])]
+            (error '+ "not a number" y)])]
         [(flonum? x)
          (cond
            [(fixnum? y)
@@ -591,7 +591,7 @@
            [(ratnum? y)
             ($fl+ x (ratnum->flonum y))]
            [else 
-            (error '+ "~s is not a number" y)])]
+            (error '+ "not a number" y)])]
         [(ratnum? x)
          (cond
            [(or (fixnum? y) (bignum? y))
@@ -606,8 +606,8 @@
               ;;; FIXME: inefficient
               (/ (+ (* n0 d1) (* n1 d0)) (* d0 d1)))]
            [else 
-            (error '+ "~s is not a number" y)])] 
-        [else (error '+ "~s is not a number" x)])))
+            (error '+ "not a number" y)])] 
+        [else (error '+ "not a number" x)])))
 
   (define binary-logand
     (lambda (x y)
@@ -618,7 +618,7 @@
            [(bignum? y)
             (foreign-call "ikrt_fxbnlogand" x y)]
            [else 
-            (error 'logand "~s is not an exact integer" y)])]
+            (error 'logand "not an exact integer" y)])]
         [(bignum? x)
          (cond
            [(fixnum? y)
@@ -626,8 +626,8 @@
            [(bignum? y) 
             (foreign-call "ikrt_bnbnlogand" x y)]
            [else
-            (error 'logand "~s is not an exact integer" y)])]
-        [else (error 'logand "~s is not an exact integer" x)])))
+            (error 'logand "not an exact integer" y)])]
+        [else (error 'logand "not an exact integer" x)])))
 
 
   (define binary-
@@ -647,7 +647,7 @@
             (let ([n ($ratnum-n y)] [d ($ratnum-d y)])
               (binary/ (binary- (binary* d x) n) d))]
            [else 
-            (error '- "~s is not a number" y)])]
+            (error '- "not a number" y)])]
         [(bignum? x)
          (cond
            [(fixnum? y)
@@ -660,7 +660,7 @@
             (let ([n ($ratnum-n y)] [d ($ratnum-d y)])
               (binary/ (binary- (binary* d x) n) d))]
            [else 
-            (error '- "~s is not a number" y)])]
+            (error '- "not a number" y)])]
         [(flonum? x)
          (cond
            [(fixnum? y)
@@ -673,7 +673,7 @@
             (let ([n ($ratnum-n y)] [d ($ratnum-d y)])
               (binary/ (binary- (binary* d x) n) d))]
            [else
-            (error '- "~s is not a number" y)])]
+            (error '- "not a number" y)])]
         [(ratnum? x)
          (let ([nx ($ratnum-n x)] [dx ($ratnum-d x)])
            (cond
@@ -684,8 +684,8 @@
                 (binary/ (binary- (binary* nx dy) (binary* ny dx))
                          (binary* dx dy)))]
              [else
-              (error '- "~s is not a number" y)]))]
-        [else (error '- "~s is not a number" x)])))
+              (error '- "not a number" y)]))]
+        [else (error '- "not a number" x)])))
 
   (define binary*
     (lambda (x y)
@@ -701,7 +701,7 @@
            [(ratnum? y) 
             (binary/ (binary* x ($ratnum-n y)) ($ratnum-d y))]
            [else 
-            (error '* "~s is not a number" y)])]
+            (error '* "not a number" y)])]
         [(bignum? x)
          (cond
            [(fixnum? y)
@@ -713,7 +713,7 @@
            [(ratnum? y) 
             (binary/ (binary* x ($ratnum-n y)) ($ratnum-d y))]
            [else 
-            (error '* "~s is not a number" y)])]
+            (error '* "not a number" y)])]
         [(flonum? x)
          (cond
            [(fixnum? y)
@@ -725,13 +725,13 @@
            [(ratnum? y) 
             (binary/ (binary* x ($ratnum-n y)) ($ratnum-d y))]
            [else
-            (error '* "~s is not a number" y)])]
+            (error '* "not a number" y)])]
         [(ratnum? x) 
          (if (ratnum? y) 
              (binary/ (binary* ($ratnum-n x) ($ratnum-n y))
                       (binary* ($ratnum-d x) ($ratnum-d y)))
              (binary* y x))]
-        [else (error '* "~s is not a number" x)])))
+        [else (error '* "not a number" x)])))
 
   (define +
     (case-lambda
@@ -741,7 +741,7 @@
        (cond
          [(fixnum? a) a]
          [(bignum? a) a]
-         [else (error '+ "~s is not a number" a)])]
+         [else (error '+ "not a number" a)])]
       [() 0]
       [(a b c d . e*)
        (let f ([ac (binary+ (binary+ (binary+ a b) c) d)]
@@ -758,7 +758,7 @@
        (cond
          [(fixnum? a) a]
          [(bignum? a) a]
-         [else (error 'logand "~s is not a number" a)])]
+         [else (error 'logand "not a number" a)])]
       [() -1]
       [(a b c d . e*)
        (let f ([ac (binary-logand (binary-logand (binary-logand a b) c) d)]
@@ -787,7 +787,7 @@
        (cond
          [(fixnum? a) a]
          [(bignum? a) a]
-         [else (error '* "~s is not a number" a)])]
+         [else (error '* "not a number" a)])]
       [() 1]
       [(a b c d . e*)
        (let f ([ac (binary* (binary* (binary* a b) c) d)]
@@ -817,20 +817,20 @@
             [(or (fixnum? y) (bignum? y)) 
              (binary-gcd x y)]
             [(number? y)
-             (error 'gcd "~s is not an exact integer" y)]
+             (error 'gcd "not an exact integer" y)]
             [else 
-             (error 'gcd "~s is not a number" y)])]
+             (error 'gcd "not a number" y)])]
          [(number? x)
-          (error 'gcd "~s is not an exact integer" x)]
+          (error 'gcd "not an exact integer" x)]
          [else 
-          (error 'gcd "~s is not a number" x)])]
+          (error 'gcd "not a number" x)])]
       [(x)
        (cond
          [(or (fixnum? x) (bignum? x)) x]
          [(number? x)
-          (error 'gcd "~s is not an exact integer" x)]
+          (error 'gcd "not an exact integer" x)]
          [else 
-          (error 'gcd "~s is not a number" x)])]
+          (error 'gcd "not a number" x)])]
       [() 0]
       [(x y z . ls) 
        (let f ([g (gcd (gcd x y) z)] [ls ls])
@@ -851,20 +851,20 @@
                (let ([g (binary-gcd x y)])
                  (binary* y (quotient x g))))]
             [(number? y)
-             (error 'lcm "~s is not an exact integer" y)]
+             (error 'lcm "not an exact integer" y)]
             [else 
-             (error 'lcm "~s is not a number" y)])]
+             (error 'lcm "not a number" y)])]
          [(number? x)
-          (error 'lcm "~s is not an exact integer" x)]
+          (error 'lcm "not an exact integer" x)]
          [else 
-          (error 'lcm "~s is not a number" x)])]
+          (error 'lcm "not a number" x)])]
       [(x)
        (cond
          [(or (fixnum? x) (bignum? x)) x]
          [(number? x)
-          (error 'lcm "~s is not an exact integer" x)]
+          (error 'lcm "not an exact integer" x)]
          [else 
-          (error 'lcm "~s is not a number" x)])]
+          (error 'lcm "not a number" x)])]
       [() 1]
       [(x y z . ls) 
        (let f ([g (lcm (lcm x y) z)] [ls ls])
@@ -884,7 +884,7 @@
            [(fixnum? y) ($fl/ x ($fixnum->flonum y))]
            [(bignum? y) ($fl/ x (bignum->flonum y))]
            [(ratnum? y) ($fl/ x (ratnum->flonum y))]
-           [else (error '/ "unspported ~s ~s" x y)])]
+           [else (error '/ "BUG: unspported" x y)])]
         [(fixnum? x)
          (cond
            [(flonum? y) ($fl/ ($fixnum->flonum x) y)]
@@ -926,7 +926,7 @@
                         (binary- 0 (quotient y g))))]))]
            [(ratnum? y) 
             (/ (* x ($ratnum-d y)) ($ratnum-n y))]
-           [else (error '/ "unsupported ~s ~s" x y)])]
+           [else (error '/ "BUG: unsupported" x y)])]
         [(bignum? x) 
          (cond
            [(fixnum? y) 
@@ -968,7 +968,7 @@
            [(flonum? y) ($fl/ (bignum->flonum x) y)]
            [(ratnum? y) 
             (binary/ (binary* x ($ratnum-n y)) ($ratnum-d y))]
-           [else (error '/ "~s is not a number" y)])]
+           [else (error '/ "not a number" y)])]
         [(ratnum? x)
          (cond
            [(ratnum? y) 
@@ -976,7 +976,7 @@
               (binary* ($ratnum-n x) ($ratnum-d y))
               (binary* ($ratnum-n y) ($ratnum-d x)))]
            [else (binary/ 1 (binary/ y x))])]
-        [else (error '/ "~s is not a number" x)])))
+        [else (error '/ "not a number" x)])))
 
   (define /
     (case-lambda
@@ -1005,7 +1005,7 @@
               [($fx= n 1) d]
               [($fx= n -1) (- d)]
               [else ($make-ratnum d n)]))]
-         [else (error '/ "unspported argument ~s" x)])]
+         [else (error '/ "BUG: unspported argument" x)])]
       [(x y z . rest)
        (let f ([a (binary/ x y)] [b z] [ls rest])
          (cond
@@ -1021,8 +1021,8 @@
                (if ($fl< x y) 
                    y
                    x)
-               (error 'flmax "~s is not a flonum" y))
-           (error 'flmax "~s is not a flonum" x))]
+               (error 'flmax "not a flonum" y))
+           (error 'flmax "not a flonum" x))]
       [(x y z . rest)
        (let f ([a (flmax x y)] [b z] [ls rest])
          (cond
@@ -1032,7 +1032,7 @@
       [(x) 
        (if (flonum? x) 
            x 
-           (error 'flmax "~s is not a number" x))]))
+           (error 'flmax "not a number" x))]))
 
   (define max
     (case-lambda
@@ -1044,15 +1044,15 @@
              (if ($fx> x y) x y)]
             [(bignum? y)
              (if (positive-bignum? y) y x)]
-            [else (error 'max "~s is not a number" y)])]
+            [else (error 'max "not a number" y)])]
          [(bignum? x)
           (cond
             [(fixnum? y)
              (if (positive-bignum? x) x y)]
             [(bignum? y)
              (if (bnbn> x y) x y)]
-            [else (error 'max "~s is not a number" y)])]
-         [else (error 'max "~s is not a number" x)])]
+            [else (error 'max "not a number" y)])]
+         [else (error 'max "not a number" x)])]
       [(x y z . rest)
        (let f ([a (max x y)] [b z] [ls rest])
          (cond
@@ -1062,7 +1062,7 @@
       [(x) 
        (if (number? x) 
            x 
-           (error 'max "~s is not a number" x))]))
+           (error 'max "not a number" x))]))
 
   (define min
     (case-lambda
@@ -1074,15 +1074,15 @@
              (if ($fx> x y) y x)]
             [(bignum? y)
              (if (positive-bignum? y) x y)]
-            [else (error 'min "~s is not a number" y)])]
+            [else (error 'min "not a number" y)])]
          [(bignum? x)
           (cond
             [(fixnum? y)
              (if (positive-bignum? x) y x)]
             [(bignum? y)
              (if (bnbn> x y) y x)]
-            [else (error 'min "~s is not a number" y)])]
-         [else (error 'min "~s is not a number" x)])]
+            [else (error 'min "not a number" y)])]
+         [else (error 'min "not a number" x)])]
       [(x y z . rest)
        (let f ([a (min x y)] [b z] [ls rest])
          (cond
@@ -1092,7 +1092,7 @@
       [(x) 
        (if (number? x) 
            x 
-           (error 'min "~s is not a number" x))]))
+           (error 'min "not a number" x))]))
 
   (define (abs x)
     (cond
@@ -1109,7 +1109,7 @@
          (if (< n 0) 
              ($make-ratnum (- n) ($ratnum-d x))
              x))]
-      [else (error 'abs "~s is not a number" x)]))
+      [else (error 'abs "not a number" x)]))
 
   (define flmin
     (case-lambda
@@ -1117,8 +1117,8 @@
        (if (flonum? x)
            (if (flonum? y) 
                (if ($fl< x y) x y)
-               (error 'flmin "~s is not a flonum" y))
-           (error 'flmin "~s is not a flonum" x))]
+               (error 'flmin "not a flonum" y))
+           (error 'flmin "not a flonum" x))]
       [(x y z . rest)
        (let f ([a (flmin x y)] [b z] [ls rest])
          (cond
@@ -1128,7 +1128,7 @@
       [(x) 
        (if (flonum? x) 
            x 
-           (error 'flmin "~s is not a flonum" x))]))
+           (error 'flmin "not a flonum" x))]))
 
   (define exact->inexact
     (lambda (x)
@@ -1138,7 +1138,7 @@
         [(ratnum? x) (ratnum->flonum x)]
         [else
          (error 'exact->inexact 
-                "~s is not an exact number" x)])))
+                "not an exact number" x)])))
 
   (define inexact
     (lambda (x)
@@ -1148,7 +1148,7 @@
         [(ratnum? x) (ratnum->flonum x)]
         [(flonum? x) x]
         [else
-         (error 'inexact "~s is not a number" x)])))
+         (error 'inexact "not a number" x)])))
 
 
   (define positive-bignum?
@@ -1166,14 +1166,14 @@
     (cond
       [(fixnum? x) ($fxeven? x)]
       [(bignum? x) (even-bignum? x)]
-      [else (error 'even? "~s is not an integer" x)]))
+      [else (error 'even? "not an integer" x)]))
 
   (define (odd? x)
     (not
       (cond
         [(fixnum? x) ($fxeven? x)]
         [(bignum? x) (even-bignum? x)]
-        [else (error 'odd? "~s is not an integer" x)])))
+        [else (error 'odd? "not an integer" x)])))
 
   (define bignum->string
     (lambda (x)
@@ -1194,7 +1194,7 @@
         [(bignum? x) (bignum->string x)]
         [(flonum? x) (flonum->string x)]
         [(ratnum? x) (ratnum->string x)]
-        [else (error 'number->string "~s is not a number" x)])))
+        [else (error 'number->string "not a number" x)])))
 
   (define modulo
     (lambda (n m)
@@ -1202,8 +1202,8 @@
         [(fixnum? n)
          (cond
            [(fixnum? m) ($fxmodulo n m)]
-           [else (error 'modulo "unsupported ~s" m)])]
-        [else (error 'modulo "unsupported ~s" n)])))
+           [else (error 'modulo "BUG: unsupported" m)])]
+        [else (error 'modulo "BUG: unsupported" n)])))
 
   (define-syntax mk<
     (syntax-rules ()
@@ -1212,7 +1212,7 @@
                fxrt< rtfx< bnrt< rtbn< flrt< rtfl< rtrt<)
        (let ()
          (define err
-           (lambda (x) (error 'name "~s is not a number" x)))
+           (lambda (x) (error 'name "not a number" x)))
          (define fxloopt
            (lambda (x y ls)
              (cond
@@ -1429,24 +1429,24 @@
             (if (flonum? x)
                 (if (flonum? y) 
                     ($fl< x y)
-                    (error 'fl<? "~s is not a flonum" y))
-                (error 'fl<? "~s is not a flonum" x))]
+                    (error 'fl<? "not a flonum" y))
+                (error 'fl<? "not a flonum" x))]
            [(x y z) 
             (if (flonum? x)
                 (if (flonum? y) 
                     (if (flonum? z) 
                         (and ($fl< x y) ($fl< y z))
-                        (error 'fl<? "~s is not a flonum" z))
-                    (error 'fl<? "~s is not a flonum" y))
-                (error 'fl<? "~s is not a flonum" x))]
+                        (error 'fl<? "not a flonum" z))
+                    (error 'fl<? "not a flonum" y))
+                (error 'fl<? "not a flonum" x))]
            [(x) 
             (or (flonum? x)
-                (error 'fl<? "~s is not a flonum" x))]
+                (error 'fl<? "not a flonum" x))]
            [(x y . rest) 
             (let ()
               (define (loopf a ls)
                 (unless (flonum? a) 
-                  (error 'fl<? "~s is not a flonum" a))
+                  (error 'fl<? "not a flonum" a))
                 (if (null? ls) 
                     #f
                     (loopf (car ls) (cdr ls))))
@@ -1460,10 +1460,10 @@
                                     (if ($fl< x y) 
                                         (f y (car ls) (cdr ls))
                                         (loopf (car ls) (cdr ls))))
-                                (error 'fl<? "~s is not a flonum" y)))
+                                (error 'fl<? "not a flonum" y)))
                           (loopf (car rest) (cdr rest)))
-                      (error 'fl<? "~s is not a flonum" y))
-                  (error 'fl<? "~s is not a flonum" x)))]))]))
+                      (error 'fl<? "not a flonum" y))
+                  (error 'fl<? "not a flonum" x)))]))]))
   (define-flcmp fl=? $fl=)
   (define-flcmp fl<? $fl<)
   (define-flcmp fl<=? $fl<=)
@@ -1476,8 +1476,8 @@
        (if (flonum? x)
            (if (flonum? y) 
                ($fl+ x y)
-               (error 'fl+ "~s is not a flonum" y))
-           (error 'fl+ "~s is not a flonum" x))]
+               (error 'fl+ "not a flonum" y))
+           (error 'fl+ "not a flonum" x))]
       [(x y z) 
        (fl+ (fl+ x y) z)]
       [(x y z q . rest)
@@ -1488,7 +1488,7 @@
       [(x) 
        (if (flonum? x) 
            x
-           (error 'fl+ "~s is not a flonum" x))]
+           (error 'fl+ "not a flonum" x))]
       [() (exact->inexact 0)]))
 
 
@@ -1498,8 +1498,8 @@
        (if (flonum? x)
            (if (flonum? y) 
                ($fl- x y)
-               (error 'fl- "~s is not a flonum" y))
-           (error 'fl- "~s is not a flonum" x))]
+               (error 'fl- "not a flonum" y))
+           (error 'fl- "not a flonum" x))]
       [(x y z) 
        (fl- (fl- x y) z)]
       [(x y z q . rest)
@@ -1510,7 +1510,7 @@
       [(x) 
        (if (flonum? x) 
            ($fl* -1.0 x)
-           (error 'fl+ "~s is not a flonum" x))]))
+           (error 'fl+ "not a flonum" x))]))
 
   (define fl*
     (case-lambda
@@ -1518,8 +1518,8 @@
        (if (flonum? x)
            (if (flonum? y) 
                ($fl* x y)
-               (error 'fl* "~s is not a flonum" y))
-           (error 'fl* "~s is not a flonum" x))]
+               (error 'fl* "not a flonum" y))
+           (error 'fl* "not a flonum" x))]
       [(x y z) 
        (fl* (fl* x y) z)]
       [(x y z q . rest)
@@ -1530,7 +1530,7 @@
       [(x) 
        (if (flonum? x) 
            x
-           (error 'fl* "~s is not a flonum" x))]
+           (error 'fl* "not a flonum" x))]
       [() 1.0]))
 
   (define fl/
@@ -1539,8 +1539,8 @@
        (if (flonum? x)
            (if (flonum? y) 
                ($fl/ x y)
-               (error 'fl/ "~s is not a flonum" y))
-           (error 'fl/ "~s is not a flonum" x))]
+               (error 'fl/ "not a flonum" y))
+           (error 'fl/ "not a flonum" x))]
       [(x y z) 
        (fl/ (fl/ x y) z)]
       [(x y z q . rest)
@@ -1551,7 +1551,7 @@
       [(x) 
        (if (flonum? x) 
            ($fl/ 1.0 x)
-           (error 'fl/ "~s is not a flonum" x))])) 
+           (error 'fl/ "not a flonum" x))])) 
 
   (flcmp flfl= flfx= fxfl= flbn= bnfl= $fl=)
   (flcmp flfl< flfx< fxfl< flbn< bnfl< $fl<)
@@ -1603,7 +1603,7 @@
          (foreign-call "ikrt_fxfxplus" x 1)]
         [(bignum? x)
          (foreign-call "ikrt_fxbnplus" 1 x)]
-        [else (error 'add1 "~s is not a number" x)])))
+        [else (error 'add1 "not a number" x)])))
 
   (define sub1
     (lambda (x)
@@ -1612,7 +1612,7 @@
          (foreign-call "ikrt_fxfxplus" x -1)]
         [(bignum? x)
          (foreign-call "ikrt_fxbnplus" -1 x)]
-        [else (error 'sub1 "~s is not a number" x)])))
+        [else (error 'sub1 "not a number" x)])))
 
   (define zero?
     (lambda (x)
@@ -1621,11 +1621,8 @@
         [(bignum? x) #f]
         [(flonum? x)
          (or ($fl= x 0.0) ($fl= x -0.0))]
-        [else (error 'zero? "tag=~s / ~s  is not a number" 
-                     ($fxlogand 255 
-                      ($fxsll x 2))
-                     ($fxlogand x -1)
-                     )])))
+        [else 
+         (error 'zero? "not a number" x)])))
 
   (define expt
     (lambda (n m)
@@ -1638,7 +1635,7 @@
             [else
              (binary* n (fxexpt (binary* n n) ($fxsra m 1)))])))
       (unless (number? n)
-        (error 'expt "~s is not a numebr" n))
+        (error 'expt "not a numebr" n))
       (cond
         [(fixnum? m) 
          (if ($fx>= m 0)
@@ -1655,8 +1652,8 @@
                     -1)
                 (/ 1 (expt n (- m))))]
            [else 
-            (error 'expt "(expt ~s ~s) is too big to compute" n m)])]
-        [else (error 'expt "~s is not a number" m)])))
+            (error 'expt "result is too big to compute" n m)])]
+        [else (error 'expt "not a number" m)])))
 
   (define quotient
     (lambda (x y)
@@ -1687,8 +1684,8 @@
                  (let-values ([(q r) (quotient+remainder x v)])
                    (values (inexact q) (inexact r)))]
                 [else
-                 (error 'quotient+remainder "~s is not an integer" y)]))]
-           [else (error 'quotient+remainder "~s is not a number" y)])]
+                 (error 'quotient+remainder "not an integer" y)]))]
+           [else (error 'quotient+remainder "not a number" y)])]
         [(bignum? x)
          (cond
            [(fixnum? y)
@@ -1704,16 +1701,16 @@
                  (let-values ([(q r) (quotient+remainder x v)])
                    (values (inexact q) (inexact r)))]
                 [else
-                 (error 'quotient+remainder "~s is not an integer" y)]))] 
-           [else (error 'quotient+remainder "~s is not a number" y)])]
+                 (error 'quotient+remainder "not an integer" y)]))] 
+           [else (error 'quotient+remainder "not a number" y)])]
         [(flonum? x) 
          (let ([v ($flonum->exact x)])
            (cond
              [(or (fixnum? v) (bignum? v)) 
               (let-values ([(q r) (quotient+remainder v y)])
                 (values (inexact q) (inexact r)))]
-             [else (error 'quotient+remainder "~s is not an integer" x)]))]
-        [else (error 'quotient+remainder "~s is not a number" x)])))
+             [else (error 'quotient+remainder "not an integer" x)]))]
+        [else (error 'quotient+remainder "not a number" x)])))
 
   (define positive?
     (lambda (x)
@@ -1722,7 +1719,7 @@
         [(flonum? x) ($fl> x 0.0)]
         [(bignum? x) (positive-bignum? x)]
         [(ratnum? x) (positive? ($ratnum-n x))]
-        [else (error 'positive? "~s is not a number" x)])))
+        [else (error 'positive? "not a number" x)])))
 
   (define negative?
     (lambda (x)
@@ -1731,49 +1728,49 @@
         [(flonum? x) ($fl< x 0.0)]
         [(bignum? x) (not (positive-bignum? x))]
         [(ratnum? x) (negative? ($ratnum-n x))]
-        [else (error 'negative? "~s is not a number" x)])))
+        [else (error 'negative? "not a number" x)])))
 
   (define sin
     (lambda (x)
       (cond
         [(flonum? x) (foreign-call "ikrt_fl_sin" x)]
         [(fixnum? x) (foreign-call "ikrt_fx_sin" x)]
-        [else (error 'sin "unsupported ~s" x)])))
+        [else (error 'sin "BUG: unsupported" x)])))
 
   (define cos
     (lambda (x)
       (cond
         [(flonum? x) (foreign-call "ikrt_fl_cos" x)]
         [(fixnum? x) (foreign-call "ikrt_fx_cos" x)]
-        [else (error 'cos "unsupported ~s" x)])))
+        [else (error 'cos "BUG: unsupported" x)])))
 
   (define tan
     (lambda (x)
       (cond
         [(flonum? x) (foreign-call "ikrt_fl_tan" x)]
         [(fixnum? x) (foreign-call "ikrt_fx_tan" x)]
-        [else (error 'tan "unsupported ~s" x)])))
+        [else (error 'tan "BUG: unsupported" x)])))
 
   (define asin
     (lambda (x)
       (cond
         [(flonum? x) (foreign-call "ikrt_fl_asin" x)]
         [(fixnum? x) (foreign-call "ikrt_fx_asin" x)]
-        [else (error 'asin "unsupported ~s" x)])))
+        [else (error 'asin "BUG: unsupported" x)])))
 
   (define acos
     (lambda (x)
       (cond
         [(flonum? x) (foreign-call "ikrt_fl_acos" x)]
         [(fixnum? x) (foreign-call "ikrt_fx_acos" x)]
-        [else (error 'acos "unsupported ~s" x)])))
+        [else (error 'acos "BUG: unsupported" x)])))
 
   (define atan
     (lambda (x)
       (cond
         [(flonum? x) (foreign-call "ikrt_fl_atan" x)]
         [(fixnum? x) (foreign-call "ikrt_fx_atan" x)]
-        [else (error 'atan "unsupported ~s" x)])))
+        [else (error 'atan "BUG: unsupported" x)])))
 
   (define sqrt
     (lambda (x)
@@ -1782,25 +1779,25 @@
         [(fixnum? x) (foreign-call "ikrt_fx_sqrt" x)]
         [(bignum? x) (error 'sqrt "BUG: bignum sqrt not implemented")]
         [(ratnum? x) (/ (sqrt ($ratnum-n x)) (sqrt ($ratnum-d x)))]
-        [else (error 'sqrt "unsupported ~s" x)])))
+        [else (error 'sqrt "BUG: unsupported" x)])))
 
   (define flsqrt
     (lambda (x)
       (if (flonum? x) 
           (foreign-call "ikrt_fl_sqrt" x)
-          (error 'flsqrt "~s is not a flonum" x))))
+          (error 'flsqrt "not a flonum" x))))
 
   (define flzero?
     (lambda (x)
       (if (flonum? x) 
           ($flzero? x)
-          (error 'flzero? "~s is not a flonum" x))))
+          (error 'flzero? "not a flonum" x))))
 
   (define flnegative?
     (lambda (x)
       (if (flonum? x) 
           ($fl< x 0.0)
-          (error 'flnegative? "~s is not a flonum" x))))
+          (error 'flnegative? "not a flonum" x))))
 
   (define exact-integer-sqrt
     (lambda (x)
@@ -1824,7 +1821,7 @@
       (cond
         [(fixnum? x) 
          (cond
-           [($fx< x 0) (error who "invalid argument ~s" x)]
+           [($fx< x 0) (error who "invalid argument" x)]
            [($fx= x 0) (values 0 0)]
            [($fx< x 4) (values 1 ($fx- x 1))]
            [($fx< x 9) (values 2 ($fx- x 4))]
@@ -1834,8 +1831,8 @@
          (cond
            [($bignum-positive? x) 
             (bnsqrt x 23170 (quotient x 23170))]
-           [else (error who "invalid argument ~s" x)])]
-        [else (error who "invalid argument ~s" x)])))
+           [else (error who "invalid argument" x)])]
+        [else (error who "invalid argument" x)])))
 
 
   (define numerator
@@ -1844,7 +1841,7 @@
         [(ratnum? x) ($ratnum-n x)]
         [(or (fixnum? x) (bignum? x)) x]
         [(flonum? x) (flnumerator x)]
-        [else (error 'numerator "~s is not an exact integer" x)])))
+        [else (error 'numerator "not an exact integer" x)])))
 
   (define denominator
     (lambda (x)
@@ -1852,7 +1849,7 @@
         [(ratnum? x) ($ratnum-d x)]
         [(or (fixnum? x) (bignum? x)) 1]
         [(flonum? x) (fldenominator x)]
-        [else (error 'denominator "~s is not an exact integer" x)])))
+        [else (error 'denominator "not an exact integer" x)])))
 
 
   (define (floor x)
@@ -1863,14 +1860,14 @@
     (cond
       [(flonum? x) 
        (let ([e (or ($flonum->exact x)
-                    (error 'floor "~s has no real value" x))])
+                    (error 'floor "number has no real value" x))])
          (cond
            [(ratnum? e) 
             (exact->inexact (ratnum-floor e))] 
            [else x]))]
       [(ratnum? x) (ratnum-floor x)]
       [(or (fixnum? x) (bignum? x)) x]
-      [else (error 'floor "~s is not a number" x)]))
+      [else (error 'floor "not a number" x)]))
   
   (define (ceiling x)
     (define (ratnum-ceiling x)
@@ -1880,13 +1877,13 @@
     (cond
       [(flonum? x) 
        (let ([e (or ($flonum->exact x)
-                    (error 'ceiling "~s has no real value" x))])
+                    (error 'ceiling "number has no real value" x))])
          (cond
            [(ratnum? e) (exact->inexact (ratnum-ceiling e))] 
            [else x]))]
       [(ratnum? x) (ratnum-ceiling x)]
       [(or (fixnum? x) (bignum? x)) x]
-      [else (error 'ceiling "~s is not a number" x)]))
+      [else (error 'ceiling "not a number" x)]))
 
 
   (define ($ratnum-round x)
@@ -1926,35 +1923,35 @@
            (cond
              [(ratnum? e) (exact->inexact ($ratnum-round e))]
              [else x]))
-        (error 'flround "~s is not a flonum" x)))
+        (error 'flround "not a flonum" x)))
 
   (define (round x)
     (cond
       [(flonum? x) 
        (let ([e (or ($flonum->exact x) 
-                    (error 'round "~s has no real value" x))])
+                    (error 'round "number has no real value" x))])
          (cond
            [(ratnum? e) (exact->inexact ($ratnum-round e))]
            [else x]))]
       [(ratnum? x) ($ratnum-round x)]
       [(or (fixnum? x) (bignum? x)) x]
-      [else (error 'round "~s is not a number" x)]))
+      [else (error 'round "not a number" x)]))
 
   (define (truncate x)
     (cond
       [(flonum? x) 
        (let ([e (or ($flonum->exact x) 
-                    (error 'truncate "~s has no real value" x))])
+                    (error 'truncate "number has no real value" x))])
          (cond
            [(ratnum? e) (exact->inexact ($ratnum-truncate e))]
            [else x]))]
       [(ratnum? x) ($ratnum-truncate x)]
       [(or (fixnum? x) (bignum? x)) x]
-      [else (error 'truncate "~s is not a number" x)]))
+      [else (error 'truncate "not a number" x)]))
   
   (define (fltruncate x)
     (unless (flonum? x)
-      (error 'fltruncate "~s is not a flonum" x))
+      (error 'fltruncate "not a flonum" x))
     (let ([v ($flonum->exact x)])
       (cond
         [(ratnum? v) (exact->inexact ($ratnum-truncate x))]
@@ -1968,14 +1965,14 @@
            [($fx= x 1) 0]
            [($fx= x 0) (error 'log "undefined around 0")]
            [($fx> x 0) (foreign-call "ikrt_fx_log" x)]
-           [else (error 'log "negative argument ~s" x)])]
+           [else (error 'log "negative argument" x)])]
         [(flonum? x) 
          (cond
            [(>= x 0) (foreign-call "ikrt_fl_log" x)]
-           [else (error 'log "negative argument ~s" x)])]
+           [else (error 'log "negative argument" x)])]
         [(bignum? x) (log (exact->inexact x))]
         [(ratnum? x) (- (log (numerator x)) (log (denominator x)))]
-        [else (error 'log "~s is not a number" x)])))
+        [else (error 'log "not a number" x)])))
 
   (define string->number
     (lambda (x)
@@ -2005,7 +2002,7 @@
              [(#\0) 0]
              [(#\1) 1]
              [else #f])]
-          [else (error 'convert-char "invalid radix ~s" radix)]))
+          [else (error 'convert-char "invalid radix" radix)]))
       (define (parse-exponent-start x n i radix)
         (define (parse-exponent x n i radix ac) 
           (cond
@@ -2167,7 +2164,7 @@
                [else #f]))]))
       ;;;
       (unless (string? x)
-        (error 'string->number "~s is not a string" x))
+        (error 'string->number "not a string" x))
       (let ([n (string-length x)])
         (cond
           [(fx= n (string-length "+xxx.0"))
@@ -2187,46 +2184,46 @@
             (foreign-call "ikrt_fxrandom" n) 
             (if (fx= n 1) 
                 0
-                (error 'random "incorrect argument ~s" n)))
-        (error 'random "~s is not a fixnum" n)))
+                (error 'random "incorrect argument" n)))
+        (error 'random "not a fixnum" n)))
 
 
   (define (shift-right-arithmetic n m who) 
     (unless (fixnum? m)
-      (error who "shift amount ~s is not a fixnum"))
+      (error who "shift amount is not a fixnum"))
     (cond
       [(fixnum? n) 
        (cond
          [($fx>= m 0) ($fxsra n m)]
-         [else (error who "offset ~s must be non-negative" m)])]
+         [else (error who "offset must be non-negative" m)])]
       [(bignum? n) 
        (cond
          [($fx> m 0)  
           (foreign-call "ikrt_bignum_shift_right" n m)]
          [($fx= m 0) n]
-         [else (error who "offset ~s must be non-negative" m)])]
-      [else (error who "~s is not an exact integer" n)]))
+         [else (error who "offset must be non-negative" m)])]
+      [else (error who "not an exact integer" n)]))
 
   (define (sra n m)
     (shift-right-arithmetic n m 'sra))
 
   (define (shift-left-logical n m who) 
     (unless (fixnum? m)
-      (error who "shift amount ~s is not a fixnum"))
+      (error who "shift amount is not a fixnum"))
     (cond
       [(fixnum? n)
        (cond
          [($fx> m 0) 
           (foreign-call "ikrt_fixnum_shift_left" n m)]
          [($fx= m 0) n]
-         [else (error who "offset ~s must be non-negative" m)])]
+         [else (error who "offset must be non-negative" m)])]
       [(bignum? n) 
        (cond
          [($fx> m 0) 
           (foreign-call "ikrt_bignum_shift_left" n m)]
          [($fx= m 0) n]
-         [else (error who "offset ~s must be non-negative" m)])]
-      [else (error who "~s is not an exact integer" n)]))
+         [else (error who "offset must be non-negative" m)])]
+      [else (error who "not an exact integer" n)]))
 
   (define (sll n m)
     (shift-left-logical n m 'sll))
@@ -2238,7 +2235,7 @@
   (define (bitwise-arithmetic-shift n m)
     (define who 'bitwise-arithmetic-shift)
     (unless (fixnum? m)
-      (error who "shift amount ~s is not a fixnum"))
+      (error who "shift amount is not a fixnum"))
     (cond
       [(fixnum? n)
        (cond
@@ -2248,7 +2245,7 @@
          [else
           (let ([m^ (- m)])
             (unless (fixnum? m^) 
-              (error who "shift amount ~s is too big" m))
+              (error who "shift amount is too big" m))
             ($fxsra n m^))])]
       [(bignum? n)
        (cond
@@ -2258,9 +2255,9 @@
          [else
           (let ([m^ (- m)])
             (unless (fixnum? m^) 
-              (error who "shift amount ~s is too big" m))
+              (error who "shift amount is too big" m))
             (foreign-call "ikrt_bignum_shift_right" n m^))])]
-      [else (error who "~s is not an exact integer" n)]))
+      [else (error who "not an exact integer" n)]))
 
   (define (exp x) 
     (cond
@@ -2269,7 +2266,7 @@
        (if ($fx= x 0) 1 (flexp (fixnum->flonum x)))]
       [(bignum? x) (flexp (bignum->flonum x))]
       [(ratnum? x) (flexp (ratnum->flonum x))]
-      [else (error 'exp "~s is not a number" x)]))
+      [else (error 'exp "not a number" x)]))
 
 
   )
@@ -2402,7 +2399,6 @@
              (string d0) "." (list->string d*) 
              "e" (fixnum->string (- expt 1)))])))
     (define (flo->string pos? m e p)
-    ;  (printf "compo: ~s ~s ~s\n" m e p)
       (let-values ([(expt digits) (flonum->digits m e 10 p 2 10)])
          (format-flonum pos? expt digits)))
     (define (flonum->string x)
@@ -2425,7 +2421,7 @@
        (foreign-call "ikrt_bytevector_to_flonum" 
          (string->utf8 x))]
       [else 
-       (error 'string->flonum "~s is not a string" x)])) )
+       (error 'string->flonum "not a string" x)])) )
 
 (library (ikarus rationalize)
   (export rationalize)
@@ -2467,21 +2463,21 @@
               (if (flfinite? eps) (go x eps) +nan.0)]
              [(or (fixnum? eps) (bignum? eps) (ratnum? eps))
               (go x eps)]
-             [else (error who "~s is not a number" eps)])
+             [else (error who "not a number" eps)])
            (cond
              [(flonum? eps) 
               (if (flfinite? eps) x +nan.0)]
              [(or (fixnum? eps) (bignum? eps) (ratnum? eps))
               x]
-             [else (error who "~s is not a number" eps)]))]
+             [else (error who "not a number" eps)]))]
       [(or (fixnum? x) (bignum? x) (ratnum? x))
        (cond
          [(flonum? eps) 
           (if (flfinite? eps) (go x eps) +nan.0)]
          [(or (fixnum? eps) (bignum? eps) (ratnum? eps))
           (go x eps)]
-         [else (error who "~s is not a number" eps)])]
-      [else (error who "~s is not a number" x)])))
+         [else (error who "not a number" eps)])]
+      [else (error who "not a number" x)])))
 
 
 (library (ikarus r6rs-fu div/mod)
@@ -2493,9 +2489,9 @@
   (define (div-and-mod x y) 
     (define who 'div-and-mod)
     (unless (integer? x)
-      (error who "~s is not an integer" x))
+      (error who "not an integer" x))
     (unless (and (integer? y) (not (= y 0)))
-      (error who "~s is not an integer" y))
+      (error who "not an integer" y))
     (if (> x 0) 
         (quotient+remainder x y)
         (if (> y 0) 
@@ -2515,9 +2511,9 @@
   (define (div0-and-mod0 x y) 
     (define who 'div0-and-mod0)
     (unless (integer? x)
-      (error who "~s is not an integer" x))
+      (error who "not an integer" x))
     (unless (and (integer? y) (not (= y 0)))
-      (error who "~s is not an integer" y))
+      (error who "not an integer" y))
     (let-values ([(d m) (div-and-mod x y)])
       (if (> y 0) 
           (if (< m (/ y 2))
diff --git a/scheme/ikarus.pairs.ss b/scheme/ikarus.pairs.ss
index 42de0d6..7559b88 100644
--- a/scheme/ikarus.pairs.ss
+++ b/scheme/ikarus.pairs.ss
@@ -24,13 +24,13 @@
   (define set-car!
     (lambda (x y) 
       (unless (pair? x)
-        (error 'set-car! "~s is not a pair" x))
+        (error 'set-car! "not a pair" x))
       ($set-car! x y)))
   
   (define set-cdr! 
     (lambda (x y)
       (unless (pair? x)
-        (error 'set-cdr! "~s is not a pair" x))
+        (error 'set-cdr! "not a pair" x))
       ($set-cdr! x y)))
 
   (define-syntax cxr
@@ -50,7 +50,7 @@
        (begin
          (define name*
            (lambda (x) 
-             ((cxr (error 'name* "invalid list structure ~s" x) ops** ...)
+             ((cxr (error 'name* "invalid list structure" x) ops** ...)
               x)))
          ...)]))
 
diff --git a/scheme/ikarus.posix.ss b/scheme/ikarus.posix.ss
index 7445e32..44e67f6 100644
--- a/scheme/ikarus.posix.ss
+++ b/scheme/ikarus.posix.ss
@@ -24,13 +24,13 @@
   (define waitpid
     (lambda (pid)
       (unless (fixnum? pid)
-        (error 'waitpid "~s is not a fixnum" pid))
+        (error 'waitpid "not a fixnum" pid))
       (foreign-call "ikrt_waitpid" pid)))
 
   (define system
     (lambda (x)
       (unless (string? x)
-        (error 'system "~s is not a string" x))
+        (error 'system "not a string" x))
       (let ([rv (foreign-call "ik_system"
                   (string->utf8 x))])
         (if (fx= rv -1)
@@ -40,7 +40,7 @@
   (define file-exists?
     (lambda (x)
       (unless (string? x)
-        (error 'file-exists? "filename ~s is not a string" x))
+        (error 'file-exists? "filename is not a string" x))
       (let ([v (foreign-call "ikrt_file_exists" 
                   (string->utf8 x))])
         (cond
@@ -48,19 +48,19 @@
           [else
            (error 'file-exists?
                   (case v
-                    [(1) "the path ~s contains a non-directory"]
-                    [(2) "the path ~s is too long"]
-                    [(3) "the path ~s is not accessible"]
-                    [(4) "the path ~s contains too many symbolic links"]
-                    [(5) "internal access error while accessing ~s"]
-                    [(6) "IO error encountered while accessing ~s"]
-                    [else "Unknown error in ~s"])
+                    [(1) "the path contains a non-directory"]
+                    [(2) "the path is too long"]
+                    [(3) "the path is not accessible"]
+                    [(4) "the path contains too many symbolic links"]
+                    [(5) "internal access error while accessing"]
+                    [(6) "IO error encountered while accessing"]
+                    [else "Unknown error"])
                   x)]))))
 
   (define delete-file
     (lambda (x)
       (unless (string? x)
-        (error 'delete-file "filename ~s is not a string" x))
+        (error 'delete-file "filename is not a string" x))
       (let ([v (foreign-call "ikrt_delete_file"
                  (string->utf8 x))])
         (case v
@@ -68,17 +68,17 @@
           [else
            (error 'delete-file
                   (case v
-                    [(1) "the path ~s contains a non-directory"]
-                    [(2) "the path ~s is too long"]
-                    [(3) "the file ~s does not exist"]
-                    [(4) "the path ~s is not accessible"]
-                    [(5) "the path ~s contains too many symbolic links"]
-                    [(6) "you do not have permissions to delete ~s"]
-                    [(7) "device ~s is busy"]
-                    [(8) "IO error encountered while deleting ~s"]
-                    [(9) "~s is in a read-only file system"]
-                    [(10) "internal access error while deleting ~s"]
-                    [else "Unknown error while deleting ~s"])
+                    [(1) "the path contains a non-directory"]
+                    [(2) "the path is too long"]
+                    [(3) "the file does not exist"]
+                    [(4) "the path is not accessible"]
+                    [(5) "the path contains too many symbolic links"]
+                    [(6) "you do not have permissions to delete file"]
+                    [(7) "device is busy"]
+                    [(8) "IO error encountered while deleting"]
+                    [(9) "is in a read-only file system"]
+                    [(10) "internal access error while deleting"]
+                    [else "Unknown error while deleting"])
                   x)]))))
 
   (define env
@@ -88,16 +88,16 @@
           [(key) 
            (if (string? key)
                (foreign-call "ikrt_getenv" key)
-               (error 'env "the key: ~s is not a string" key))]
+               (error 'env "the key is not a string" key))]
           [(key val) (env key val #t)]
           [(key val overwrite?)
            (if (string? key)
                (if (string? val)
                    (unless (foreign-call "ikrt_setenv" key val overwrite?)
-                     (error 'env "failed to set ~s to ~s" key val))
-                   (error 'env "the value: ~s is not a string" val))
-               (error 'env "the key: ~s is not a string" key))]))
-      (define busted (lambda args (error 'env "busted!")))
+                     (error 'env "failed" key val))
+                   (error 'env "the value is not a string" val))
+               (error 'env "the key is not a string" key))]))
+      (define busted (lambda args (error 'env "BUG: busted!")))
       busted))
 
 
diff --git a/scheme/ikarus.predicates.ss b/scheme/ikarus.predicates.ss
index ea8f48d..3aff4ff 100644
--- a/scheme/ikarus.predicates.ss
+++ b/scheme/ikarus.predicates.ss
@@ -109,7 +109,7 @@
         [(sys:ratnum? x) #t]
         [(sys:flonum? x) #f]
         [else 
-         (error 'exact? "~s is not a number" x)])))
+         (error 'exact? "not a number" x)])))
   
 
   (define inexact?
@@ -120,7 +120,7 @@
         [(sys:bignum? x) #f]
         [(sys:ratnum? x) #f]
         [else 
-         (error 'inexact? "~s is not a number" x)])))
+         (error 'inexact? "not a number" x)])))
 
   (define finite?
     (lambda (x)
@@ -130,7 +130,7 @@
         [(sys:bignum? x) #t]
         [(sys:ratnum? x) #t]
         [else 
-         (error 'finite? "~s is not a number" x)])))
+         (error 'finite? "not a number" x)])))
 
   (define infinite?
     (lambda (x)
@@ -140,7 +140,7 @@
         [(sys:bignum? x) #f]
         [(sys:ratnum? x) #f]
         [else 
-         (error 'infinite? "~s is not a number" x)])))
+         (error 'infinite? "not a number" x)])))
 
   (define nan?
     (lambda (x)
@@ -150,7 +150,7 @@
         [(sys:bignum? x) #f]
         [(sys:ratnum? x) #f]
         [else 
-         (error 'nan? "~s is not a number" x)])))
+         (error 'nan? "not a number" x)])))
 
 
 
@@ -191,8 +191,8 @@
               #t
               (if (sys:boolean? y) 
                   #f
-                  (error 'boolean=? "~s is not a boolean" y)))
-          (error 'boolean=? "~s is not a boolean" x))))
+                  (error 'boolean=? "not a boolean" y)))
+          (error 'boolean=? "not a boolean" x))))
 
 
   (define symbol=?
@@ -202,8 +202,8 @@
               #t
               (if (sys:symbol? y) 
                   #f
-                  (error 'symbol=? "~s is not a symbol" y)))
-          (error 'symbol=? "~s is not a symbol" x))))
+                  (error 'symbol=? "not a symbol" y)))
+          (error 'symbol=? "not a symbol" x))))
 
   (module (equal?)
     (define vector-loop
diff --git a/scheme/ikarus.pretty-print.ss b/scheme/ikarus.pretty-print.ss
index 4ed10b5..2b53235 100644
--- a/scheme/ikarus.pretty-print.ss
+++ b/scheme/ikarus.pretty-print.ss
@@ -26,7 +26,7 @@
       [(mbox? x)   (mbox-length x)]
       [(vbox? x)   (vbox-length x)]
       [(fbox? x)   (fbox-length x)]
-      [else (error 'boxify "invalid box ~s" x)]))
+      [else (error 'boxify "invalid box" x)]))
   (define (boxify x)
     (define (conc . a*)
       (let ([n 
@@ -437,7 +437,7 @@
         [(mbox? x)   (output-mbox x p col)]
         [(vbox? x)   (output-vbox x p col)]
         [(fbox? x)   (output-fbox x p col)]
-        [else (error 'pretty-print-output "invalid ~s" x)]))
+        [else (error 'pretty-print-output "invalid" x)]))
     (f x p 0)
     (newline p))
   ;;;
@@ -586,7 +586,7 @@
       [(x p)
        (if (output-port? p)
            (pretty x p)
-           (error 'pretty-print "~s is not an output port" p))]))
+           (error 'pretty-print "not an output port" p))]))
   (set-fmt! 'quote '(read-macro . "'"))
   (set-fmt! 'unquote '(read-macro . ","))
   (set-fmt! 'unquote-splicing '(read-macro . ",@"))
@@ -648,7 +648,7 @@
       [(x p)
        (if (output-port? p)
            (pretty x p)
-           (error 'pretty-print "~s is not an output port" p))])))
+           (error 'pretty-print "not an output port" p))])))
 
 (test '(384 7384 83947 893478 9137489 3894789 134789314 79817238
         97314897 318947138974 981374 89137489 1374897 13498713
@@ -679,5 +679,5 @@
                      (with-input-from-file fname read))])
               (if (equal? x y)
                   (f (fxadd1 i))
-                  (error 'test-file "mismatch\n\n~s\n\n~s" x y)))))))))
+                  (error 'test-file "mismatch" x y)))))))))
 
diff --git a/scheme/ikarus.promises.ss b/scheme/ikarus.promises.ss
index 9eb8b8b..b56b1c6 100644
--- a/scheme/ikarus.promises.ss
+++ b/scheme/ikarus.promises.ss
@@ -6,12 +6,12 @@
 
   (define (force x)
     (unless (procedure? x) 
-      (error 'force "~s is not a procedure" x))
+      (error 'force "not a procedure" x))
     (x))
 
   (define (make-promise proc)
     (unless (procedure? proc)
-      (error 'make-promise "~s is not a procedure" proc))
+      (error 'make-promise "not a procedure" proc))
     (let ([results #f])
       (lambda () 
         (if results
diff --git a/scheme/ikarus.reader.ss b/scheme/ikarus.reader.ss
index e3bde26..52b445a 100644
--- a/scheme/ikarus.reader.ss
+++ b/scheme/ikarus.reader.ss
@@ -59,7 +59,7 @@
           ls]
          [else
           (unread-char c p)
-          (error 'tokenize "invalid identifier syntax: ~a" 
+          (error 'tokenize "invalid identifier syntax" 
                  (list->string (reverse (cons c ls))))]))))
   (define tokenize-string
     (lambda (ls p)
@@ -95,12 +95,12 @@
                                (cons (integer->char n) ls) p)]
                             [else
                              (error 'tokenize
-                               "invalid char ~a in escape sequence"
+                               "invalid char in escape sequence"
                                c)]))))]
                    [else 
                     (error 'tokenize
-                      "invalid char ~a in escape sequence" c)]))]
-              [else (error 'tokenize "invalid string escape \\~a" c)]))]
+                      "invalid char in escape sequence" c)]))]
+              [else (error 'tokenize "invalid string escape" c)]))]
          [else
           (tokenize-string (cons c ls) p)]))))
   (define skip-comment
@@ -128,10 +128,12 @@
                     [(eof-object? c) '(datum . ...)]
                     [(delimiter? c)  '(datum . ...)]
                     [else 
-                     (error 'tokenize "invalid syntax ...~a" c)]))]
+                     (error 'tokenize "invalid syntax"
+                            (string-append "..." (string c)))]))]
                [else
                 (unread-char c p)
-                (error 'tokenize "invalid syntax ..~a" c)]))]
+                (error 'tokenize "invalid syntax"
+                       (string-append ".." (string c)))]))]
           [else 
            (cons 'datum 
              (tokenize-decimal-no-digits p '(#\.) #f))]))))
@@ -143,17 +145,19 @@
           (cond
            [(eof-object? c) d]
            [(delimiter? c)  d]
-           [else (error 'tokenize "invalid character after #\\~a" str)]))]
+           [else (error 'tokenize "invalid character after sequence"
+                        (string-append (string c) str))]))]
        [else
         (let ([c (read-char p)])
           (cond
             [(eof-object? c) 
-             (error 'tokenize "invalid eof in the middle of #\\~a" str)]
+             (error 'tokenize "invalid eof in the middle of expected sequence" str)]
             [($char= c (string-ref str i))
              (tokenize-char* (fxadd1 i) str p d)]
             [else 
              (error 'tokenize
-                    "invalid char ~a while scanning #\\~a" c str)]))])))
+                    "invalid char while scanning string"
+                    c str)]))])))
   (define tokenize-char-seq
     (lambda (p str d)
       (let ([c (peek-char p)])
@@ -163,7 +167,7 @@
           [($char= (string-ref str 1) c) 
            (read-char p)
            (tokenize-char*  2 str p d)]
-          [else (error 'tokenize "invalid syntax near #\\~a~a" 
+          [else (error 'tokenize "invalid syntax" 
                        (string-ref str 0) c)]))))
   (define tokenize-char
     (lambda (p)
@@ -201,14 +205,16 @@
                         [else
                          (error 'tokenize "invalid character sequence")]))))]
                [else
-                (error 'tokenize "invalid character sequence #\\x~a" n)]))]
+                (error 'tokenize "invalid character sequence"
+                       (string-append "#\\" (string n)))]))]
           [else
            (let ([n (peek-char p)])
              (cond
                [(eof-object? n) (cons 'datum c)]
                [(delimiter? n)  (cons 'datum c)]
                [else 
-                (error 'tokenize "invalid syntax #\\~a~a" c n)]))]))))
+                (error 'tokenize "invalid syntax"
+                       (string-append "#\\" (string c n)))]))]))))
   (define (hex x)
     (cond
       [(and ($char<= #\0 x) ($char<= x #\9))
@@ -265,7 +271,7 @@
     (let ([c (read-char p)])
       (cond
         [(eof-object? c)
-         (error 'tokenize "invalid eof insize ~a" caller)]
+         (error 'tokenize "invalid eof inside" caller)]
         [(char-whitespace? c)
          (skip-whitespace p caller)]
         [else c])))
@@ -278,13 +284,15 @@
            (cond
              [(eof-object? c) '(datum . #t)]
              [(delimiter? c)  '(datum . #t)]
-             [else (error 'tokenize "invalid syntax near #~a" c)]))]
+             [else (error 'tokenize 
+                     (format "invalid syntax near #~a" c))]))]
         [(memq c '(#\f #\F)) 
          (let ([c (peek-char p)])
            (cond
              [(eof-object? c) '(datum . #f)]
              [(delimiter? c)  '(datum . #f)]
-             [else (error 'tokenize "invalid syntax near #~a" c)]))]
+             [else (error 'tokenize 
+                     (format "invalid syntax near #~a" c))]))]
         [($char= #\\ c) (tokenize-char p)]
         [($char= #\( c) 'vparen]
         [($char= #\' c) '(macro . syntax)]
@@ -303,17 +311,20 @@
            (when (eof-object? e)
              (error 'tokenize "invalid eof near #!"))
            (unless ($char= #\e e)
-             (error 'tokenize "invalid syntax near #!~a" e))
+             (error 'tokenize
+               (format "invalid syntax near #!~a" e)))
            (let ([o (read-char p)])
              (when (eof-object? o)
                (error 'tokenize "invalid eof near #!e"))
              (unless ($char= #\o o)
-               (error 'tokenize "invalid syntax near #!e~a" o))
+               (error 'tokenize 
+                 (format "invalid syntax near #!e~a" o)))
              (let ([f (read-char p)])
                (when (eof-object? f)
                  (error 'tokenize "invalid syntax near #!eo"))
                (unless ($char= #\f f)
-                 (error 'tokenize "invalid syntax near #!eo~a" f))
+                 (error 'tokenize 
+                   (format "invalid syntax near #!eo~a" f)))
                (cons 'datum (eof-object)))))]
         [(digit? c) 
          (tokenize-hashnum p (char->num c))]
@@ -329,7 +340,7 @@
                       (reverse (tokenize-bar p '())))]
                    [else 
                     (error 'tokenize
-                      "invalid char ~a inside gensym" c)])])
+                      "invalid char inside gensym" c)])])
               (cons 'datum (gensym id0)))]
         [($char= #\{ c)
          (let* ([c (skip-whitespace p "gensym")]
@@ -343,7 +354,7 @@
                       (reverse (tokenize-bar p '())))]
                    [else 
                     (error 'tokenize
-                      "invalid char ~a inside gensym" c)])]
+                      "invalid char inside gensym" c)])]
                 [c (skip-whitespace p "gensym")])
            (cond
              [($char= #\} c)
@@ -361,7 +372,7 @@
                           (reverse (tokenize-bar p '())))]
                        [else 
                         (error 'tokenize
-                          "invalid char ~a inside gensym" c)])])
+                          "invalid char inside gensym" c)])])
                 (let ([c (skip-whitespace p "gensym")])
                   (cond
                     [($char= #\} c)
@@ -370,7 +381,7 @@
                         id0 id1))]
                     [else
                      (error 'tokenize
-                        "invalid char ~a inside gensym" c)])))]))]
+                        "invalid char inside gensym" c)])))]))]
         [($char= #\v c)
          (let ([c (read-char p)])
            (cond
@@ -383,13 +394,16 @@
                        [($char= c #\() 'vu8]
                        [(eof-object? c) 
                         (error 'tokenize "invalid eof object after #vu8")]
-                       [else (error 'tokenize "invalid sequence #vu8~a" c)]))]
+                       [else (error 'tokenize 
+                               (format "invalid sequence #vu8~a" c))]))]
                   [(eof-object? c) 
                    (error 'tokenize "invalid eof object after #vu")]
-                  [else (error 'tokenize "invalid sequence #vu~a" c)]))]
+                  [else (error 'tokenize 
+                           (format "invalid sequence #vu~a" c))]))]
              [(eof-object? c) 
               (error 'tokenize "invalid eof object after #v")]
-             [else (error 'tokenize "invalid sequence #v~a" c)]))]
+             [else (error 'tokenize
+                     (format "invalid sequence #v~a" c))]))]
         [(memq c '(#\e #\E)) 
          (cons 'datum (tokenize-exactness-mark p (list c #\#) 'e))]
         [(memq c '(#\i #\I)) 
@@ -407,7 +421,8 @@
          '(cons 'datum ($fasl-read p))]
         [else 
          (unread-char c p)
-         (error 'tokenize "invalid syntax #~a" c)])))
+         (error 'tokenize 
+            (format "invalid syntax #~a" c))])))
   (define (tokenize-exactness-mark p ls exact?)
     (let ([c (read-char p)])
       (cond
@@ -630,7 +645,7 @@
          [(#\0) 0]
          [(#\1) 1]
          [else #f])]
-      [else (error 'radix-digit "invalid radix ~s" radix)]))
+      [else (error 'radix-digit "invalid radix" radix)]))
   (define (read-char* p ls str who) 
     (let f ([i 0] [ls ls])
       (let ([c (read-char p)])
@@ -641,18 +656,21 @@
              [(delimiter? c) (unread-char c p)]
              [else
               (unread-char c p)
-              (error 'tokenize "invalid ~a: ~s" who 
-                (list->string (reverse (cons c ls))))])]
+              (error 'tokenize 
+                (format "invalid ~a: ~s" who 
+                  (list->string (reverse (cons c ls)))))])]
           [else
            (cond
              [(eof-object? c) 
-              (error 'tokenize "invalid eof inside ~a" who)]
+              (error 'tokenize
+                (format "invalid eof inside ~a" who))]
              [(char=? c (string-ref str i)) 
               (f (add1 i) (cons c ls))]
              [else 
               (unread-char c p)
-              (error 'tokenize "invalid ~a: ~s" who
-                 (list->string (reverse (cons c ls))))])]))))
+              (error 'tokenize 
+                (format "invalid ~a: ~s" who
+                  (list->string (reverse (cons c ls)))))])]))))
   (define (tokenize-integer/nan/inf-no-digits p ls)
     (let ([c (read-char p)])
       (cond
@@ -682,7 +700,7 @@
          (tokenize-decimal-no-digits p (cons c ls) exact?)]
         [else (num-error "invalid sequence" (cons c ls))])))
   (define (num-error str ls)
-    (error 'read "invalid numeric sequence ~a"
+    (error 'read "invalid numeric sequence"
       (list->string (reverse ls))))
   (define (tokenize-hashnum p n)
     (let ([c (read-char p)])
@@ -695,7 +713,7 @@
          (tokenize-hashnum p (fx+ (fx* n 10) (char->num c)))]
         [else
          (unread-char c p)
-         (error 'tokenize "invalid char ~a while inside a #n mark/ref" c)])))
+         (error 'tokenize "invalid char while inside a #n mark/ref" c)])))
   (define tokenize-bar
     (lambda (p ac)
       (let ([c (read-char p)])
@@ -726,8 +744,9 @@
                   (let ([c (read-char p)])
                     (cond
                       [(eof-object? c) 
-                       (error 'tokenize "invalid eof after ~a"
-                         (list->string (reverse ac)))]
+                       (error 'tokenize 
+                         (format "invalid eof after ~a"
+                           (list->string (reverse ac))))]
                       [($char= #\; c)
                        (cons 'datum 
                          (string->symbol 
@@ -738,14 +757,16 @@
                        (lambda (v0)
                          (f (+ (* v 16) v0) (cons c ac)))]
                       [else 
-                       (error 'tokenize "invalid sequence ~a"
+                       (error 'tokenize "invalid sequence"
                          (list->string (cons c (reverse ac))))]))))]
              [else
               (unread-char c p) 
-              (error 'tokenize "invalid sequence \\x~a" c)]))]
+              (error 'tokenize 
+                 (format "invalid sequence \\x~a" c))]))]
         [else 
          (unread-char c p) 
-         (error 'tokenize "invalid sequence \\~a" c)])))
+         (error 'tokenize
+           (format "invalid sequence \\~a" c))])))
   (define tokenize/c
     (lambda (c p)
       (cond
@@ -809,7 +830,7 @@
          (tokenize-backslash p)]
         [else
          (unread-char c p) 
-         (error 'tokenize "invalid syntax ~a" c)])))
+         (error 'tokenize "invalid syntax" c)])))
 
   (define tokenize
     (lambda (p)
@@ -851,7 +872,8 @@
                [(eq? t 'dot)
                 (error 'read "cannot have two dots in a list")]
                [else
-                (error 'read "expecting ~a, got ~a" end t)])))]
+                (error 'read 
+                  (format "expecting ~a, got ~a" end t))])))]
          [(eq? t 'hash-semi)
           (let-values ([(ignored locs k) (read-expr p locs k)])
             (read-list-rest p locs k end mis))]
@@ -918,10 +940,11 @@
            (cond
              [(fixnum? a)
               (unless (and (fx<= 0 a) (fx<= a 255))
-                (error 'read "invalid value ~s in a bytevector" a))
+                (error 'read 
+                  (format "invalid value ~s in a bytevector" a)))
               ($bytevector-set! v i a)
               (bytevector-put v k ($fxsub1 i) ($cdr ls))]
-             [else (error 'read "invalid value ~s is a bytevector" a)]))])))
+             [else (error 'read "invalid value inside a bytevector" a)]))])))
   (define read-vector
     (lambda (p locs k count ls)
       (let ([t (tokenize p)])
@@ -994,7 +1017,7 @@
                    (lambda (x)
                      (let ([loc (cdr x)])
                        (when (loc-set? loc)
-                         (error 'read "duplicate mark ~s" n))
+                         (error 'read "duplicate mark" n))
                        (set-loc-value! loc expr)
                        (set-loc-set?! loc #t)
                        (values expr locs k)))]
@@ -1012,9 +1035,10 @@
                  (let ([loc (make-loc #f #f)])
                    (let ([locs (cons (cons n loc) locs)])
                      (values loc locs k)))]))]
-           [else (error 'read "invalid token! ~s" t)])]
+           [else (error 'read "invalid token" t)])]
         [else
-         (error 'read "unexpected ~s found" t)])))
+         (error 'read 
+           (format "unexpected ~s found" t))])))
 
   (define read-expr
     (lambda (p locs k)
@@ -1028,7 +1052,7 @@
     (lambda (x)
        (let ([loc (cdr x)])
          (unless (loc-set? loc)
-           (error 'read "referenced mark ~s not set" (car x)))
+           (error 'read "referenced mark is not set" (car x)))
          (when (loc? (loc-value loc))
            (let f ([h loc] [t loc])
              (if (loc? h)
@@ -1076,7 +1100,7 @@
       [(p)
        (if (input-port? p)
            (tokenize p)
-           (error 'read-token "~s is not an input port" p))]))
+           (error 'read-token "not an input port" p))]))
 
   (define read
     (case-lambda
@@ -1084,14 +1108,14 @@
       [(p)
        (if (input-port? p)
            (my-read p)
-           (error 'read "~s is not an input port" p))]))
+           (error 'read "not an input port" p))]))
 
   (define comment-handler
     (make-parameter
       (lambda (x) (void))
       (lambda (x)
         (unless (procedure? x)
-          (error 'comment-handler "~s is not a procedure" x))
+          (error 'comment-handler "not a procedure" x))
         x)))
 
   )
diff --git a/scheme/ikarus.records.procedural.ss b/scheme/ikarus.records.procedural.ss
index a5505f6..d74cd23 100644
--- a/scheme/ikarus.records.procedural.ss
+++ b/scheme/ikarus.records.procedural.ss
@@ -40,7 +40,7 @@
 
   (define (record-rtd x)
     (define (err x)
-      (error 'record-rtd "~s is not a record" x))
+      (error 'record-rtd "not a record" x))
     (if ($struct? x)
         (let ([rtd ($struct-rtd x)])
           (if (rtd? rtd)
@@ -53,32 +53,32 @@
   (define (record-type-name x)
     (if (rtd? x)
         (rtd-name x)
-        (error 'record-type-name "~s is not an rtd" x)))
+        (error 'record-type-name "not an rtd" x)))
 
   (define (record-type-parent x)
     (if (rtd? x)
         (rtd-parent x)
-        (error 'record-type-parent "~s is not an rtd" x)))
+        (error 'record-type-parent "not an rtd" x)))
 
   (define (record-type-uid x)
     (if (rtd? x)
         (rtd-uid x)
-        (error 'record-type-uid "~s is not an rtd" x)))
+        (error 'record-type-uid "not an rtd" x)))
 
   (define (record-type-sealed? x)
     (if (rtd? x)
         (rtd-sealed? x)
-        (error 'record-type-sealed? "~s is not an rtd" x)))
+        (error 'record-type-sealed? "not an rtd" x)))
 
   (define (record-type-opaque? x)
     (if (rtd? x)
         (rtd-opaque? x)
-        (error 'record-type-opaque? "~s is not an rtd" x)))
+        (error 'record-type-opaque? "not an rtd" x)))
 
   (define (record-type-generative? x)
     (if (rtd? x)
         (not (rtd-sealed? x))
-        (error 'record-type-generative? "~s is not an rtd" x)))
+        (error 'record-type-generative? "not an rtd" x)))
 
   (define (record-type-field-names x)
     (if (rtd? x)
@@ -90,7 +90,7 @@
                   (begin
                     (vector-set! x i (cdr (vector-ref v i)))
                     (f x v n (fxadd1 i)))))))
-        (error 'record-type-field-names "~s is not an rtd" x)))
+        (error 'record-type-field-names "not an rtd" x)))
 
 
   (module (make-record-type-descriptor)
@@ -101,7 +101,7 @@
           #f #f #f parent sealed? opaque? uid fields))
     (define (convert-fields sv)
       (unless (vector? sv) 
-        (error who "invalid fields argument ~s" sv))
+        (error who "invalid fields argument" sv))
       (let ([n2 (vector-length sv)])
         (let ([v (make-vector n2)])
           (let f ([i 0])
@@ -112,16 +112,16 @@
                       (if (pair? x) 
                           (let ([name (car x)])
                             (unless (and (null? (cdr x)) (symbol? name))
-                              (error who "invalid fields argument ~s" sv))
+                              (error who "invalid fields argument" sv))
                             (vector-set! v i
                               (cons (case m/u
                                       [(mutable)   #t]
                                       [(immutable) #f]
                                       [else 
-                                       (error who "invalid fields argument ~s" sv)]) 
+                                       (error who "invalid fields argument" sv)]) 
                                     name)))
-                          (error who "invalid fields argument ~s" sv)))
-                    (error who "invalid fields argument ~s" sv)))
+                          (error who "invalid fields argument" sv)))
+                    (error who "invalid fields argument" sv)))
               (f (add1 i))))
           v)))
     (define generate-rtd
@@ -129,7 +129,7 @@
         (cond
           [(rtd? parent)
            (when (rtd-sealed? parent) 
-             (error who "cannot extend sealed parent ~s" parent))
+             (error who "cannot extend sealed parent" parent))
            (make-rtd-aux name parent uid sealed? 
              (or opaque? (rtd-opaque? parent))
              (rtd-size parent)
@@ -137,7 +137,7 @@
           [(eqv? parent #f) 
            (make-rtd-aux name parent uid sealed? opaque? 0
              (convert-fields fields))]
-          [else (error who "~s is not a valid parent" parent)])))
+          [else (error who "not a valid parent" parent)])))
     (define (same-fields-as-rtd? fields rtd)
       (let* ([fv (rtd-fields rtd)]
              [n (vector-length fv)])
@@ -178,17 +178,17 @@
     (define make-record-type-descriptor
       (lambda (name parent uid sealed? opaque? fields)
         (unless (symbol? name)
-          (error who "~s is not a valid record type name" name))
+          (error who "not a valid record type name" name))
         (unless (boolean? sealed?)
-          (error who "~s is not a valid sealed? argument" sealed?))
+          (error who "not a valid sealed? argument" sealed?))
         (unless (boolean? opaque?)
-          (error who "~s is not a valid opaque? argument" opaque?))
+          (error who "not a valid opaque? argument" opaque?))
         (cond
           [(symbol? uid) 
            (make-nongenerative-rtd name parent uid sealed? opaque? fields)]
           [(eqv? uid #f) 
            (generate-rtd name parent uid sealed? opaque? fields)]
-          [else (error who "~s is not a valid uid" uid)]))))
+          [else (error who "not a valid uid" uid)]))))
 
   (define-struct rcd (rtd prcd proc))
 
@@ -201,9 +201,9 @@
 
   (define (rtd-subtype? rtd parent-rtd) 
     (unless (rtd? rtd) 
-      (error 'rtd-subtype? "~s is not an rtd" rtd))
+      (error 'rtd-subtype? "not an rtd" rtd))
     (unless (rtd? parent-rtd) 
-      (error 'rtd-substype? "~s is not an rtd" parent-rtd))
+      (error 'rtd-substype? "not an rtd" parent-rtd))
     (or (eq? rtd parent-rtd)
         (is-parent-of? parent-rtd rtd)))
         
@@ -211,20 +211,20 @@
     (lambda (rtd prcd protocol)
       (define who 'make-record-constructor-descriptor)
       (unless (rtd? rtd)
-        (error who "~s is not a record type descriptor" rtd))
+        (error who "not a record type descriptor" rtd))
       (unless (or (not protocol) (procedure? protocol))
-        (error who "invalid protocol ~s" protocol))
+        (error who "invalid protocol" protocol))
       (let ([prtd (rtd-parent rtd)])
         (cond
           [(not prcd) 
            (make-rcd rtd #f protocol)]
           [(rcd? prcd) 
            (unless (is-parent-of? (rcd-rtd prcd) rtd)
-             (error who "descriptor ~s does not apply to ~s" 
+             (error who "descriptor does not apply" 
                     prcd rtd))
            (make-rcd rtd prcd protocol)]
           [else
-           (error who "~s is not a valid record constructor descriptor" prcd)]))))
+           (error who "not a valid record constructor descriptor" prcd)]))))
 
   (define (record-constructor rcd)
     (define who 'record-constructor)
@@ -235,7 +235,7 @@
                        (let ([n (rtd-size main-rtd)])
                          (unless (= (length flds) size)
                            (error 'record-constructor 
-                              "expecting ~s args, got ~s" n flds))
+                              "expecting args, got" n flds))
                          (let ([r ($make-struct main-rtd n)])
                            (let f ([i 0] [r r] [flds flds] [f* f*])
                              (cond
@@ -258,15 +258,15 @@
                         (lambda flds
                           (unless (= (length flds) n) 
                             (error 'record-constructor 
-                               "expecting ~s args, got ~s" n flds))
+                               "expecting args, got" n flds))
                           (apply (p (cons flds f*)) fmls))))
                     (lambda flds
                       (unless (= (length flds) n) 
                          (error 'record-constructor 
-                           "expecting ~s args, got ~s" n flds))
+                           "expecting args, got" n flds))
                       ((p (cons flds f*))))))))))
     (unless (rcd? rcd)
-      (error who "~s is not a record constructor descriptor" rcd))
+      (error who "not a record constructor descriptor" rcd))
     (let ([rtd (rcd-rtd rcd)]
           [prcd (rcd-prcd rcd)]
           [proto (rcd-proc rcd)])
@@ -276,61 +276,61 @@
   (define (record-accessor rtd k) 
     (define who 'record-accessor)
     (unless (rtd? rtd)
-      (error who "~s is not an rtd" rtd))
+      (error who "not an rtd" rtd))
     (unless (and (fixnum? k) (fx>= k 0)) 
-      (error who "~s is not a valid index" k))
+      (error who "not a valid index" k))
     (let ([sz (rtd-size rtd)]
           [p (rtd-parent rtd)])
       (let ([i (if p (+ k (rtd-size p)) k)])
         (unless (fx< i sz) 
-          (error who "~s is not a valid index" k))
+          (error who "not a valid index" k))
         (lambda (x) 
           (cond
             [($struct/rtd? x rtd) ($struct-ref x i)]
             [($struct? x)
              (let ([xrtd ($struct-rtd x)])
                (unless (rtd? xrtd) 
-                 (error who "~s is not of type ~s" x rtd))
+                 (error who "invalid type" x rtd))
                (let f ([prtd (rtd-parent xrtd)] [rtd rtd] [x x] [i i])
                  (cond
                    [(eq? prtd rtd) ($struct-ref x i)]
                    [(not prtd) 
-                    (error who "~s is not of type ~s" x rtd)]
+                    (error who "invalid type" x rtd)]
                    [else (f (rtd-parent prtd) rtd x i)])))]
-            [else (error who "~s is not of type ~s" x rtd)])))))
+            [else (error who "invalid type" x rtd)])))))
 
   (define (record-mutator rtd k) 
     (define who 'record-mutator)
     (unless (rtd? rtd)
-      (error who "~s is not an rtd" rtd))
+      (error who "not an rtd" rtd))
     (unless (and (fixnum? k) (fx>= k 0)) 
-      (error who "~s is not a valid index" k))
+      (error who "not a valid index" k))
     (let ([sz (rtd-size rtd)]
           [p (rtd-parent rtd)])
       (let ([i (if p (+ k (rtd-size p)) k)])
         (unless (fx< i sz) 
-          (error who "~s is not a valid index" k))
+          (error who "not a valid index" k))
         (unless (car (vector-ref (rtd-fields rtd) k))
-          (error who "field ~s of ~s is not mutable" k rtd))
+          (error who "field is not mutable" k rtd))
         (lambda (x v) 
           (cond
             [($struct/rtd? x rtd) ($struct-set! x i v)]
             [($struct? x)
              (let ([xrtd ($struct-rtd x)])
                (unless (rtd? xrtd) 
-                 (error who "~s is not of type ~s" x rtd))
+                 (error who "invalid type" x rtd))
                (let f ([prtd (rtd-parent xrtd)] [rtd rtd] [x x] [i i] [v v])
                  (cond
                    [(eq? prtd rtd) ($struct-set! x i v)]
                    [(not prtd) 
-                    (error who "~s is not of type ~s" x rtd)]
+                    (error who "invalid type" x rtd)]
                    [else (f (rtd-parent prtd) rtd x i v)])))]
-            [else (error who "~s is not of type ~s" x rtd)])))))
+            [else (error who "invalid type" x rtd)])))))
 
   (define (record-predicate rtd) 
     (define who 'record-predicate)
     (unless (rtd? rtd)
-      (error who "~s is not an rtd" rtd))
+      (error who "not an rtd" rtd))
     (let ([sz (rtd-size rtd)]
           [p (rtd-parent rtd)])
        (lambda (x) 
@@ -350,14 +350,14 @@
   (define (record-field-mutable? rtd k) 
     (define who 'record-field-mutable?)
     (unless (rtd? rtd)
-      (error who "~s is not an rtd" rtd))
+      (error who "not an rtd" rtd))
     (unless (and (fixnum? k) (fx>= k 0)) 
-      (error who "~s is not a valid index" k))
+      (error who "not a valid index" k))
     (let ([sz (rtd-size rtd)]
           [p (rtd-parent rtd)])
       (let ([i (if p (+ k (rtd-size p)) k)])
         (unless (fx< i sz) 
-          (error who "~s is not a valid index" k))
+          (error who "not a valid index" k))
         (car (vector-ref (rtd-fields rtd) k)))))
 
   (set-rtd-printer! (type-descriptor rtd)
diff --git a/scheme/ikarus.sort.ss b/scheme/ikarus.sort.ss
index e3158b7..b097592 100644
--- a/scheme/ikarus.sort.ss
+++ b/scheme/ikarus.sort.ss
@@ -61,23 +61,23 @@
 
   (define (list-sort <? ls) 
     (unless (procedure? <?)
-      (error 'list-sort "~s is not a procedure" <?))
+      (error 'list-sort "not a procedure" <?))
     (sort-tail <? ls (length ls)))
 
   (define (vector-sort <? v)
     ;;; FIXME: improve
     (unless (procedure? <?)
-      (error 'vector-sort "~s is not a procedure" <?))
+      (error 'vector-sort "not a procedure" <?))
     (unless (vector? v)
-      (error 'vector-sort "~s is not a vector" v))
+      (error 'vector-sort "not a vector" v))
     (list->vector 
       (sort-tail <? (vector->list v) (vector-length v))))
 
   (define (vector-sort! <? v) 
     (unless (procedure? <?)
-      (error 'vector-sort! "~s is not a procedure" <?))
+      (error 'vector-sort! "not a procedure" <?))
     (unless (vector? v)
-      (error 'vector-sort! "~s is not a vector" v))
+      (error 'vector-sort! "not a vector" v))
     (let f ([i 0] [v v] 
             [ls (sort-tail <? (vector->list v) (vector-length v))])
       (unless (null? ls) 
diff --git a/scheme/ikarus.strings.ss b/scheme/ikarus.strings.ss
index c345c82..87dfdbf 100644
--- a/scheme/ikarus.strings.ss
+++ b/scheme/ikarus.strings.ss
@@ -20,18 +20,18 @@
   (define string-length
     (lambda (x)
       (unless (string? x)
-        (error 'string-length "~s is not a string" x))
+        (error 'string-length "not a string" x))
       ($string-length x)))
 
 
   (define (string-ref s i)
     (unless (string? s) 
-      (error 'string-ref "~s is not a string" s))
+      (error 'string-ref "not a string" s))
     (unless (fixnum? i)
-      (error 'string-ref "~s is not a valid index" i))
+      (error 'string-ref "not a valid index" i))
     (unless (and ($fx< i ($string-length s))
                  ($fx<= 0 i))
-      (error 'string-ref "index ~s is out of range for ~s" i s))
+      (error 'string-ref "index is out of range" i s))
     (let ([c ($string-ref s i)])
       (unless (char? c)
         (error 'string-ref "BUG: got a non-char"))
@@ -41,14 +41,14 @@
   (define string-set! 
     (lambda (s i c) 
       (unless (string? s) 
-        (error 'string-set! "~s is not a string" s))
+        (error 'string-set! "not a string" s))
       (unless (fixnum? i)
-        (error 'string-set! "~s is not a valid index" i))
+        (error 'string-set! "not a valid index" i))
       (unless (and ($fx< i ($string-length s))
                    ($fx>= i 0))
-        (error 'string-set! "index ~s is out of range for ~s" i s))
+        (error 'string-set! "index is out of range" i s))
       (unless (char? c)
-        (error 'string-set! "~s is not a character" c))
+        (error 'string-set! "not a character" c))
       ($string-set! s i c)))
   
   (define make-string
@@ -64,13 +64,13 @@
         (case-lambda
           [(n) 
            (unless (and (fixnum? n) (fx>= n 0))
-             (error 'make-string "~s is not a valid length" n))
+             (error 'make-string "not a valid length" n))
            (fill! ($make-string n) 0 n (integer->char 0))]
           [(n c)
            (unless (and (fixnum? n) (fx>= n 0))
-             (error 'make-string "~s is not a valid length" n))
+             (error 'make-string "not a valid length" n))
            (unless (char? c)
-             (error 'make-string "~s is not a character" c))
+             (error 'make-string "not a character" c))
            (fill! ($make-string n) 0 n c)]))
         make-string))
 
@@ -82,7 +82,7 @@
                 (cond
                  [(null? ls) n]
                  [(char? ($car ls)) (length ($cdr ls) ($fx+ n 1))]
-                 [else (error 'string "~s is not a character" ($car ls))]))]
+                 [else (error 'string "not a character" ($car ls))]))]
              [loop 
               (lambda (s ls i n)
                 (cond
@@ -106,16 +106,16 @@
     (define substring
        (lambda (s n m)
          (unless (string? s)
-           (error 'substring "~s is not a string" s))
+           (error 'substring "not a string" s))
          (let ([len ($string-length s)])
            (unless (and (fixnum? n)
                         ($fx>= n 0)
                         ($fx< n len))
-             (error 'substring "~s is not a valid start index for ~s" n s))
+             (error 'substring "not a valid start index" n s))
            (unless (and (fixnum? m)
                         ($fx>= m 0)
                         ($fx<= m len))
-             (error 'substring "~s is not a valid end index for ~s" m s))
+             (error 'substring "not a valid end index" m s))
            (let ([len ($fx- m n)])
              (if ($fx<= len 0)
                  ""
@@ -125,7 +125,7 @@
     (lambda (s)
       (if (string? s)
           (substring s 0 (string-length s))
-          (error 'string-copy "~s is not a string" s))))
+          (error 'string-copy "not a string" s))))
   
   (module (string=?)
     (define bstring=?
@@ -145,13 +145,13 @@
         (or (null? s*)
             (let ([a ($car s*)])
               (unless (string? a)
-                (error 'string=? "~s is not a string" a))
+                (error 'string=? "not a string" a))
               (if ($fx= n ($string-length a))
                   (and (strings=? s ($cdr s*) n)
                        (bstring=? s a 0 n))
                   (check-strings-and-return-false ($cdr s*)))))))
     (define (err x)
-      (error 'string=? "~s is not a string" x))
+      (error 'string=? "not a string" x))
     (define string=?
       (case-lambda
         [(s s1) 
@@ -185,10 +185,10 @@
                              [(string? (car s*)) 
                               (f (cdr s*))]
                              [else 
-                              (error who "~s is not a string" 
+                              (error who "not a string" 
                                 (car s*))]))))
-                     (error who "~s is not a string" s2))])))
-          (error who "~s is not a string" s1)))
+                     (error who "not a string" s2))])))
+          (error who "not a string" s1)))
   
   (define ($string<? s1 s2)
     (let ([n1 ($string-length s1)]
@@ -252,8 +252,8 @@
        (if (string? s1)
            (if (string? s2) 
                ($string<? s1 s2)
-               (error 'string<? "~s is not a string" s2))
-           (error 'string<? "~s is not a string" s2))]
+               (error 'string<? "not a string" s2))
+           (error 'string<? "not a string" s2))]
       [(s . s*) 
        (string-cmp 'string<? $string<? s s*)]))
 
@@ -263,8 +263,8 @@
        (if (string? s1)
            (if (string? s2) 
                ($string<=? s1 s2)
-               (error 'string<=? "~s is not a string" s2))
-           (error 'string<=? "~s is not a string" s2))]
+               (error 'string<=? "not a string" s2))
+           (error 'string<=? "not a string" s2))]
       [(s . s*) 
        (string-cmp 'string<=? $string<=? s s*)]))
 
@@ -274,8 +274,8 @@
        (if (string? s1)
            (if (string? s2) 
                ($string>? s1 s2)
-               (error 'string>? "~s is not a string" s2))
-           (error 'string>? "~s is not a string" s2))]
+               (error 'string>? "not a string" s2))
+           (error 'string>? "not a string" s2))]
       [(s . s*) 
        (string-cmp 'string>? $string>? s s*)]))
 
@@ -285,15 +285,15 @@
        (if (string? s1)
            (if (string? s2) 
                ($string>=? s1 s2)
-               (error 'string>=? "~s is not a string" s2))
-           (error 'string>=? "~s is not a string" s2))]
+               (error 'string>=? "not a string" s2))
+           (error 'string>=? "not a string" s2))]
       [(s . s*) 
        (string-cmp 'string>=? $string>=? s s*)]))
 
   (define string->list
     (lambda (x)
       (unless (string? x)
-        (error 'string->list "~s is not a string" x))
+        (error 'string->list "not a string" x))
       (let f ([x x] [i ($string-length x)] [ac '()])
         (cond
           [($fxzero? i) ac]
@@ -310,13 +310,13 @@
                       (if (pair? h)
                           (if (not (eq? h t))
                               (race ($cdr h) ($cdr t) ls ($fx+ n 2))
-                              (error 'reverse "circular list ~s" ls))
+                              (error 'reverse "circular list" ls))
                           (if (null? h)
                               ($fx+ n 1)
-                              (error 'reverse "~s is not a proper list" ls))))
+                              (error 'reverse "not a proper list" ls))))
                    (if (null? h)
                        n
-                       (error 'reverse "~s is not a proper list" ls))))]
+                       (error 'reverse "not a proper list" ls))))]
               [fill
                (lambda (s i ls)
                  (cond
@@ -324,7 +324,7 @@
                    [else
                     (let ([c ($car ls)])
                       (unless (char? c)
-                        (error 'list->string "~s is not a character" c))
+                        (error 'list->string "not a character" c))
                       ($string-set! s i c)
                       (fill s ($fxadd1 i) (cdr ls)))]))])
        (lambda (ls)
@@ -341,7 +341,7 @@
           [else
            (let ([a ($car s*)])
              (unless (string? a) 
-               (error 'string-append "~s is not a string" a))
+               (error 'string-append "not a string" a))
              (length* ($cdr s*) ($fx+ n ($string-length a))))])))
     (define fill-string
       (lambda (s a si sj ai)
@@ -371,9 +371,9 @@
       (case-lambda
         [(p v) 
          (unless (procedure? p) 
-           (error who "~s is not a procedure" p))
+           (error who "not a procedure" p))
          (unless (string? v) 
-           (error who "~s is not a string" v))
+           (error who "not a string" v))
          (let f ([p p] [v v] [i 0] [n (string-length v)])
            (cond
              [($fx= i n) (void)]
@@ -382,14 +382,14 @@
               (f p v ($fxadd1 i) n)]))]
         [(p v0 v1) 
          (unless (procedure? p) 
-           (error who "~s is not a procedure" p))
+           (error who "not a procedure" p))
          (unless (string? v0) 
-           (error who "~s is not a string" v0))
+           (error who "not a string" v0))
          (unless (string? v1) 
-           (error who "~s is not a string" v1))
+           (error who "not a string" v1))
          (let ([n (string-length v0)])
            (unless ($fx= n ($string-length v1))
-             (error who "length mismatch between ~s and ~s" v0 v1))
+             (error who "length mismatch" v0 v1))
            (let f ([p p] [v0 v0] [v1 v1] [i 0] [n n])
              (cond
                [($fx= i n) (void)]
@@ -398,19 +398,19 @@
                 (f p v0 v1 ($fxadd1 i) n)])))]
         [(p v0 v1 . v*) 
          (unless (procedure? p) 
-           (error who "~s is not a procedure" p))
+           (error who "not a procedure" p))
          (unless (string? v0) 
-           (error who "~s is not a string" v0))
+           (error who "not a string" v0))
          (unless (string? v1) 
-           (error who "~s is not a string" v1))
+           (error who "not a string" v1))
          (let ([n (string-length v0)])
            (unless ($fx= n ($string-length v1))
-             (error who "length mismatch between ~s and ~s" v0 v1))
+             (error who "length mismatch" v0 v1))
            (let f ([v* v*] [n n])
              (unless (null? v*) 
                (let ([a ($car v*)])
                  (unless (string? a) 
-                   (error who "~s is not a string" a))
+                   (error who "not a string" a))
                  (unless ($fx= ($string-length a) n) 
                    (error who "length mismatch")))
                (f ($cdr v*) n)))
@@ -428,9 +428,9 @@
 
   (define (string-fill! v fill)
     (unless (string? v) 
-      (error 'string-fill! "~s is not a vector" v))
+      (error 'string-fill! "not a vector" v))
     (unless (char? fill)
-      (error 'string-fill! "~s is not a character" fill))
+      (error 'string-fill! "not a character" fill))
     (let f ([v v] [i 0] [n ($string-length v)] [fill fill])
       (unless ($fx= i n) 
         ($string-set! v i fill)
diff --git a/scheme/ikarus.structs.ss b/scheme/ikarus.structs.ss
index 74e475d..69d59f7 100644
--- a/scheme/ikarus.structs.ss
+++ b/scheme/ikarus.structs.ss
@@ -74,7 +74,7 @@
   (define verify-field
     (lambda (x)
       (unless (symbol? x) 
-        (error 'make-struct-type "~s is not a valid field name" x))))
+        (error 'make-struct-type "not a valid field name" x))))
   
   (define set-fields
     (lambda (r f* i n)
@@ -95,9 +95,9 @@
     (case-lambda
       [(name fields)
        (unless (string? name)
-         (error 'make-struct-type "name must be a string, got ~s" name))
+         (error 'make-struct-type "name must be a string" name))
        (unless (list? fields)
-         (error 'make-struct-type "fields must be a list, got ~s" fields))
+         (error 'make-struct-type "fields must be a list" fields))
        (for-each verify-field fields)
        (let ([g (gensym name)])
          (let ([rtd (make-rtd name fields #f g)])
@@ -105,9 +105,9 @@
            rtd))]
       [(name fields g)
        (unless (string? name)
-         (error 'make-struct-type "name must be a string, got ~s" name))
+         (error 'make-struct-type "name must be a string" name))
        (unless (list? fields)
-         (error 'make-struct-type "fields must be a list, got ~s" fields))
+         (error 'make-struct-type "fields must be a list" fields))
        (for-each verify-field fields)
        (cond
          [(symbol-bound? g)
@@ -124,38 +124,38 @@
   (define struct-type-name
     (lambda (rtd)
       (unless (rtd? rtd)
-        (error 'struct-type-name "~s is not an rtd" rtd))
+        (error 'struct-type-name "not an rtd" rtd))
       (rtd-name rtd)))
 
   (define struct-type-symbol
     (lambda (rtd)
       (unless (rtd? rtd)
-        (error 'struct-type-symbol "~s is not an rtd" rtd))
+        (error 'struct-type-symbol "not an rtd" rtd))
       (rtd-symbol rtd)))
   
   (define struct-type-field-names
     (lambda (rtd)
       (unless (rtd? rtd)
-        (error 'struct-type-field-names "~s is not an rtd" rtd))
+        (error 'struct-type-field-names "not an rtd" rtd))
       (rtd-fields rtd)))
  
 
   (define struct-constructor
     (lambda (rtd)
       (unless (rtd? rtd)
-        (error 'struct-constructor "~s is not an rtd"))
+        (error 'struct-constructor "not an rtd"))
       (lambda args
         (let ([n (rtd-length rtd)])
           (let ([r ($make-struct rtd n)])
             (or (set-fields r args 0 n)
                 (error 'struct-constructor 
-                  "incorrect number of arguments to the constructor of ~s" 
+                  "incorrect number of arguments to the constructor" 
                   rtd)))))))
   
   (define struct-predicate
     (lambda (rtd)
       (unless (rtd? rtd)
-        (error 'struct-predicate "~s is not an rtd"))
+        (error 'struct-predicate "not an rtd"))
       (lambda (x)
         (and ($struct? x)
              (eq? ($struct-rtd x) rtd)))))
@@ -165,39 +165,39 @@
       (cond
         [(fixnum? i)
          (unless (and ($fx>= i 0) ($fx< i (rtd-length rtd)))
-           (error who "~s is out of range for rtd ~s" rtd))
+           (error who "out of range for rtd" i rtd))
          i]
         [(symbol? i)
          (letrec ([lookup
                    (lambda (n ls)
                      (cond
                        [(null? ls) 
-                        (error who "~s is not a field in ~s" rtd)]
+                        (error who "not a field" rtd)]
                        [(eq? i ($car ls)) n]
                        [else (lookup ($fx+ n 1) ($cdr ls))]))])
            (lookup 0 (rtd-fields rtd)))]
-        [else (error who "~s is not a valid index" i)])))
+        [else (error who "not a valid index" i)])))
 
   (define struct-field-accessor
     (lambda (rtd i)
       (unless (rtd? rtd)
-        (error 'struct-field-accessor "~s is not an rtd" rtd))
+        (error 'struct-field-accessor "not an rtd" rtd))
       (let ([i (field-index i rtd 'struct-field-accessor)])
         (lambda (x)
           (unless (and ($struct? x) 
                        (eq? ($struct-rtd x) rtd))
-            (error 'struct-field-accessor "~s is not of type ~s" x rtd))
+            (error 'struct-field-accessor "not of correct type" x rtd))
           ($struct-ref x i)))))
 
   (define struct-field-mutator
     (lambda (rtd i)
       (unless (rtd? rtd)
-        (error 'struct-field-mutator "~s is not an rtd" rtd))
+        (error 'struct-field-mutator "not an rtd" rtd))
       (let ([i (field-index i rtd 'struct-field-mutator)])
         (lambda (x v)
           (unless (and ($struct? x) 
                        (eq? ($struct-rtd x) rtd))
-            (error 'struct-field-mutator "~s is not of type ~s" x rtd))
+            (error 'struct-field-mutator "not of correct type" x rtd))
           ($struct-set! x i v)))))
 
   (define struct?
@@ -208,7 +208,7 @@
             (unless (null? ($cdr rest))
               (error 'struct? "too many arguments"))
             (unless (rtd? rtd)
-              (error 'struct? "~s is not an rtd"))
+              (error 'struct? "not an rtd"))
             (and ($struct? x)
                  (eq? ($struct-rtd x) rtd))))))
 
@@ -216,49 +216,49 @@
     (lambda (x)
       (if ($struct? x)
           ($struct-rtd x)
-          (error 'struct-rtd "~s is not a struct" x))))
+          (error 'struct-rtd "not a struct" x))))
 
   (define struct-length
     (lambda (x)
       (if ($struct? x)
           (rtd-length ($struct-rtd x))
-          (error 'struct-length "~s is not a struct" x))))
+          (error 'struct-length "not a struct" x))))
             
   (define struct-name
     (lambda (x)
       (if ($struct? x)
           (rtd-name ($struct-rtd x))
-          (error 'struct-name "~s is not a struct" x))))
+          (error 'struct-name "not a struct" x))))
 
   (define struct-printer
     (lambda (x)
       (if ($struct? x)
           (rtd-printer ($struct-rtd x))
-          (error 'struct-printer "~s is not a struct" x))))
+          (error 'struct-printer "not a struct" x))))
 
   (define struct-ref
     (lambda (x i)
-      (unless ($struct? x) (error 'struct-ref "~s is not a struct" x))
-      (unless (fixnum? i) (error 'struct-ref "~s is not a valid index" i))
+      (unless ($struct? x) (error 'struct-ref "not a struct" x))
+      (unless (fixnum? i) (error 'struct-ref "not a valid index" i))
       (let ([n (rtd-length ($struct-rtd x))])
         (unless (and ($fx>= i 0) ($fx< i n))
-          (error 'struct-ref "index ~s is out of range for ~s" i x))
+          (error 'struct-ref "index is out of range" i x))
         ($struct-ref x i))))
 
   (define struct-set!
     (lambda (x i v)
-      (unless ($struct? x) (error 'struct-set! "~s is not a struct" x))
-      (unless (fixnum? i) (error 'struct-set! "~s is not a valid index" i))
+      (unless ($struct? x) (error 'struct-set! "not a struct" x))
+      (unless (fixnum? i) (error 'struct-set! "not a valid index" i))
       (let ([n (rtd-length ($struct-rtd x))])
         (unless (and ($fx>= i 0) ($fx< i n))
-          (error 'struct-set! "index ~s is out of range for ~s" i x))
+          (error 'struct-set! "index is out of range" i x))
         ($struct-set! x i v))))
 
   (define (set-rtd-printer! x p)
     (unless (rtd? x)
-      (error 'set-rtd-printer! "~s is not an rtd" x))
+      (error 'set-rtd-printer! "not an rtd" x))
     (unless (procedure? p)
-      (error 'set-rtd-printer! "~s is not a procedure" p))
+      (error 'set-rtd-printer! "not a procedure" p))
     ($set-rtd-printer! x p))
 
   (set-rtd-fields! (base-rtd) '(name fields length printer symbol))
diff --git a/scheme/ikarus.symbols.ss b/scheme/ikarus.symbols.ss
index 27d0f29..a340a56 100644
--- a/scheme/ikarus.symbols.ss
+++ b/scheme/ikarus.symbols.ss
@@ -25,7 +25,7 @@
            ($make-symbol s)
            (if (symbol? s)
                ($make-symbol ($symbol-string s))
-               (error 'gensym "~s is neither a string nor a symbol" s)))]))
+               (error 'gensym "neither a string nor a symbol" s)))]))
 
   (define gensym?
     (lambda (x)
@@ -36,7 +36,7 @@
   (define top-level-value
     (lambda (x)
       (unless (symbol? x)
-        (error 'top-level-value "~s is not a symbol" x))
+        (error 'top-level-value "not a symbol" x))
       (let ([v ($symbol-value x)])
         (when ($unbound-object? v)
           (error 'eval "unbound variable" 
@@ -47,39 +47,39 @@
   (define top-level-bound?
     (lambda (x)
       (unless (symbol? x)
-        (error 'top-level-bound? "~s is not a symbol" x))
+        (error 'top-level-bound? "not a symbol" x))
       (not ($unbound-object? ($symbol-value x)))))
 
   (define set-top-level-value!
     (lambda (x v)
       (unless (symbol? x)
-        (error 'set-top-level-value! "~s is not a symbol" x))
+        (error 'set-top-level-value! "not a symbol" x))
       ($set-symbol-value! x v)))
 
   (define symbol-value
     (lambda (x)
       (unless (symbol? x)
-        (error 'symbol-value "~s is not a symbol" x))
+        (error 'symbol-value "not a symbol" x))
       (let ([v ($symbol-value x)])
         (when ($unbound-object? v)
-          (error 'symbol-value "unbound ~s" x))
+          (error 'symbol-value "unbound" x))
         v)))
 
   (define symbol-bound?
     (lambda (x)
       (unless (symbol? x)
-        (error 'symbol-bound? "~s is not a symbol" x))
+        (error 'symbol-bound? "not a symbol" x))
       (not ($unbound-object? ($symbol-value x)))))
 
   (define set-symbol-value!
     (lambda (x v)
       (unless (symbol? x)
-        (error 'set-symbol-value! "~s is not a symbol" x))
+        (error 'set-symbol-value! "not a symbol" x))
       ($set-symbol-value! x v)
       ($set-symbol-proc! x 
         (if (procedure? v) v 
             (lambda args
-              (error 'apply "~s is not a procedure" 
+              (error 'apply "not a procedure" 
                      ($symbol-value x)))))))
          
   (define reset-symbol-proc!
@@ -94,18 +94,18 @@
                       (error 'eval "unbound variable" 
                         (string->symbol
                           (symbol->string x)))
-                      (error 'apply "~s is not a procedure" v)))))))))
+                      (error 'apply "not a procedure" v)))))))))
 
   (define string->symbol
     (lambda (x)
       (unless (string? x) 
-        (error 'string->symbol "~s is not a string" x))
+        (error 'string->symbol "not a string" x))
       (foreign-call "ikrt_string_to_symbol" x)))
   
   (define symbol->string
     (lambda (x)
       (unless (symbol? x)
-        (error 'symbol->string "~s is not a symbol" x))
+        (error 'symbol->string "not a symbol" x))
       (let ([str ($symbol-string x)])
         (or str
             (let ([ct (gensym-count)])
@@ -117,8 +117,8 @@
 
   (define putprop
     (lambda (x k v)
-      (unless (symbol? x) (error 'putprop "~s is not a symbol" x))
-      (unless (symbol? k) (error 'putprop "~s is not a symbol" k))
+      (unless (symbol? x) (error 'putprop "not a symbol" x))
+      (unless (symbol? k) (error 'putprop "not a symbol" k))
       (let ([p ($symbol-plist x)])
         (cond
           [(assq k p) => (lambda (x) (set-cdr! x v))]
@@ -127,8 +127,8 @@
 
   (define getprop
     (lambda (x k)
-      (unless (symbol? x) (error 'getprop "~s is not a symbol" x))
-      (unless (symbol? k) (error 'getprop "~s is not a symbol" k))
+      (unless (symbol? x) (error 'getprop "not a symbol" x))
+      (unless (symbol? k) (error 'getprop "not a symbol" k))
       (let ([p ($symbol-plist x)])
         (cond
           [(assq k p) => cdr]
@@ -136,8 +136,8 @@
 
   (define remprop
     (lambda (x k)
-      (unless (symbol? x) (error 'remprop "~s is not a symbol" x))
-      (unless (symbol? k) (error 'remprop "~s is not a symbol" k))
+      (unless (symbol? x) (error 'remprop "not a symbol" x))
+      (unless (symbol? k) (error 'remprop "not a symbol" k))
       (let ([p ($symbol-plist x)])
         (unless (null? p)
           (let ([a ($car p)])
@@ -156,7 +156,7 @@
   (define property-list
     (lambda (x)
       (unless (symbol? x)
-        (error 'property-list "~s is not a symbol" x))
+        (error 'property-list "not a symbol" x))
       (letrec ([f 
                 (lambda (ls ac)
                   (cond
@@ -170,12 +170,12 @@
   (define gensym->unique-string
     (lambda (x)
       (unless (symbol? x)
-        (error 'gensym->unique-string "~s is not a gensym" x))
+        (error 'gensym->unique-string "not a gensym" x))
       (let ([us ($symbol-unique-string x)])
         (cond
           [(string? us) us]
           [(not us)
-           (error 'gensym->unique-string "~s is not a gensym" x)]
+           (error 'gensym->unique-string "not a gensym" x)]
           [else
            (let f ([x x])
              (let ([id (uuid)])
@@ -189,7 +189,7 @@
       "g"
       (lambda (x)
         (unless (string? x)
-          (error 'gensym-prefix "~s is not a string" x))
+          (error 'gensym-prefix "not a string" x))
         x)))
   
   (define gensym-count
@@ -197,7 +197,7 @@
       0
       (lambda (x)
         (unless (and (fixnum? x) ($fx>= x 0))
-          (error 'gensym-count "~s is not a valid count" x))
+          (error 'gensym-count "not a valid count" x))
         x)))
   
   (define print-gensym
@@ -205,7 +205,7 @@
       #t
       (lambda (x)
         (unless (or (boolean? x) (eq? x 'pretty))
-          (error 'print-gensym "~s is not in #t|#f|pretty" x))
+          (error 'print-gensym "not in #t|#f|pretty" x))
         x)))
 
   )
diff --git a/scheme/ikarus.timer.ss b/scheme/ikarus.timer.ss
index 523ab6c..b7a68ec 100644
--- a/scheme/ikarus.timer.ss
+++ b/scheme/ikarus.timer.ss
@@ -100,7 +100,7 @@
        (time-it #f proc)]
       [(message proc)
        (unless (procedure? proc)
-         (error 'time-it "~s is not a procedure" proc))
+         (error 'time-it "not a procedure" proc))
        (let* ([t0 (mk-stats)]
               [t1 (mk-stats)]
               [bytes-min (bytes-minor)]
diff --git a/scheme/ikarus.trace.ss b/scheme/ikarus.trace.ss
index 01d38ae..5c57542 100644
--- a/scheme/ikarus.trace.ss
+++ b/scheme/ikarus.trace.ss
@@ -81,7 +81,7 @@
              (unless (eq? (cdr a) v)
                (unless (procedure? v)
                  (error 'trace
-                        "the top-level value of ~s is ~s (not a procedure)"
+                        "the top-level value is not a procedure"
                      s v))
                (let ([p (make-traced-procedure s v)])
                  (set-car! a v)
@@ -89,11 +89,10 @@
                  (set-symbol-value! s p)))))]
         [else
          (unless (symbol-bound? s)
-           (error 'trace "~s is unbound" s))
+           (error 'trace "unbound" s))
          (let ([v (symbol-value s)])
            (unless (procedure? v)
-             (error 'trace "the top-level value of ~s is ~s (not a procedure)"
-                    s v))
+             (error 'trace "the top-level value is not a procedure" s v))
            (let ([p (make-traced-procedure s v)])
              (set! traced-symbols 
                (cons (cons s (cons v p)) traced-symbols))
diff --git a/scheme/ikarus.transcoders.ss b/scheme/ikarus.transcoders.ss
index 76e6ceb..149f691 100644
--- a/scheme/ikarus.transcoders.ss
+++ b/scheme/ikarus.transcoders.ss
@@ -73,7 +73,7 @@
                      ($fxlogor #b10000000 ($fxlogand b #b111111)))
                    (f bv str ($fxadd1 i) ($fx+ j 4) n)])))])))
       (unless (string? str) 
-        (error 'string->utf8 "~s is not a string" str))
+        (error 'string->utf8 "not a string" str))
       (fill-utf8-bytevector
         ($make-bytevector (utf8-string-size str))
         str)))
@@ -105,12 +105,12 @@
                            [(eq? mode 'replace) 
                             (f x i j ($fxadd1 n) mode)]
                            [else
-                            (error who "invalid byte sequence ~s ~s
-                                   in idx ~s of ~s" b0 b1 i bv)]))]
+                            (error who "invalid byte sequence at idx of bytevector"
+                                   b0 b1 i bv)]))]
                       [(eq? mode 'ignore) n]
                       [(eq? mode 'replace) ($fxadd1 n)]
                       [else
-                       (error who "invalid byte ~s near end of bytevector" b0)]))]
+                       (error who "invalid byte near end of bytevector" b0)]))]
                  [($fx= ($fxsra b0 4) #b1110)
                   (cond
                     [($fx< ($fx+ i 2) j) 
@@ -123,7 +123,7 @@
                           (f x ($fxadd1 i) j n mode)]
                          [(eq? mode 'replace)
                           (f x ($fxadd1 i) j ($fxadd1 n) mode)]
-                         [else (error who "invalid sequence ~s ~s ~s" b0 b1 b2)]))]
+                         [else (error who "invalid sequence" b0 b1 b2)]))]
                     [(eq? mode 'ignore) (f x ($fxadd1 i) j n mode)]
                     [(eq? mode 'replace) (f x ($fxadd1 i) j ($fxadd1 n) mode)]
                     [else (error who "incomplete char sequence")])]
@@ -140,14 +140,13 @@
                           (f x ($fxadd1 i) j n mode)]
                          [(eq? mode 'replace)
                           (f x ($fxadd1 i) j ($fxadd1 n) mode)]
-                         [else (error who "invalid sequence ~s ~s ~s ~s" b0 b1 b2 b3)]))]
+                         [else (error who "invalid sequence" b0 b1 b2 b3)]))]
                     [(eq? mode 'ignore) (f x ($fxadd1 i) j n mode)]
                     [(eq? mode 'replace) (f x ($fxadd1 i) j ($fxadd1 n) mode)]
                     [else (error who "incomplete char sequence")])]
                  [(eq? mode 'ignore) (f x ($fxadd1 i) j n mode)]
                  [(eq? mode 'replace) (f x ($fxadd1 i) j ($fxadd1 n) mode)]
-                 [else (error who "invalid byte ~s at index ~s of ~s" 
-                              b0 i x)]))])))
+                 [else (error who "invalid byte at index of bytevector" b0 i x)]))])))
       (define (fill str bv mode)
         (let f ([str str] [x bv] [i 0] [j ($bytevector-length bv)] [n 0] [mode mode])
           (cond
@@ -243,7 +242,7 @@
         [(bv handling-mode)
          (unless (memq handling-mode '(ignore replace raise)) 
            (error 'decode-utf8-bytevector
-                  "~s is not a valid handling mode"
+                  "not a valid handling mode"
                   handling-mode))
          (convert bv handling-mode)])))
 
diff --git a/scheme/ikarus.unicode-data.ss b/scheme/ikarus.unicode-data.ss
index 8a6be26..7a423ad 100644
--- a/scheme/ikarus.unicode-data.ss
+++ b/scheme/ikarus.unicode-data.ss
@@ -63,12 +63,12 @@
     (if (char? c) 
         (vector-ref unicode-categories-name-vector
           (fxlogand 63 (lookup-char-info c)))
-        (error 'char-general-category "~s is not a char" c)))
+        (error 'char-general-category "not a char" c)))
 
   (define (char-has-property? c prop-val who)
     (if (char? c) 
         (not (fxzero? (fxlogand (lookup-char-info c) prop-val)))
-        (error who "~s is not a char" c)))
+        (error who "not a char" c)))
 
   (define (unicode-printable-char? c) 
     (char-has-property? c constituent-property 'unicode-printable-char?))
@@ -98,28 +98,42 @@
     (if (char? x) 
         ($fixnum->char
           (convert-char x char-downcase-adjustment-vector))
-        (error 'char-downcase "~s is not a character" x)))
+        (error 'char-downcase "not a character" x)))
 
   (define (char-upcase x)
     (if (char? x) 
         ($fixnum->char
           (convert-char x char-upcase-adjustment-vector))
-        (error 'char-downcase "~s is not a character" x)))
+        (error 'char-downcase "not a character" x)))
   
   (define (char-titlecase x)
     (if (char? x) 
         ($fixnum->char
           (convert-char x char-titlecase-adjustment-vector))
-        (error 'char-downcase "~s is not a character" x)))
+        (error 'char-downcase "not a character" x)))
 
   (define (char-foldcase x)
     (if (char? x)
         ($fixnum->char ($fold x))
-        (error 'char-downcase "~s is not a character" x)))
+        (error 'char-downcase "not a character" x)))
 
   (define ($fold x) 
     (convert-char x char-foldcase-adjustment-vector))
 
+  (define (char-ci-loop c0 ls p? who) 
+    (or (null? ls)
+        (let ([c1 (car ls)])
+          (unless (char? c1) (error who "not a char" c1))
+          (let ([c1 ($fold c1)])
+            (if (p? c0 c1) 
+                (char-ci-loop c1 (cdr ls) p? who)
+                (let f ([ls (cdr ls)] [who who])
+                  (cond
+                    [(null? ls) #f]
+                    [(char? (car ls)) 
+                     (f (cdr ls) who)]
+                    [else (error who "not a char" (car ls))])))))))
+
   (define char-ci=? 
     (case-lambda 
       [(x y) 
@@ -127,11 +141,14 @@
            (or (eq? x y)
                (if (char? y)
                    ($fx= ($fold x) ($fold y))
-                   (error 'char-ci=? "~s is not a char" y)))
-           (error 'char-ci=? "~s is not a char" x))]
+                   (error 'char-ci=? "not a char" y)))
+           (error 'char-ci=? "not a char" x))]
       [(x)
-       (or (char? x) (error 'char-ci=? "~s is not a char" x))]
-      [ls (error 'char-ci=? "not supported ~s" ls)]))
+       (or (char? x) (error 'char-ci=? "not a char" x))]
+      [(x . x*) 
+       (if (char? x) 
+           (char-ci-loop x x* char=? 'char-ci=?)
+           (error 'char-ci=? "not a char" x))]))
 
   (define char-ci<? 
     (case-lambda 
@@ -140,11 +157,14 @@
            (or (eq? x y)
                (if (char? y)
                    ($fx< ($fold x) ($fold y))
-                   (error 'char-ci<? "~s is not a char" y)))
-           (error 'char-ci<? "~s is not a char" x))]
+                   (error 'char-ci<? "not a char" y)))
+           (error 'char-ci<? "not a char" x))]
       [(x)
-       (or (char? x) (error 'char-ci<? "~s is not a char" x))]
-      [ls (error 'char-ci<? "not supported ~s" ls)]))
+       (or (char? x) (error 'char-ci<? "not a char" x))]
+      [(x . x*) 
+       (if (char? x) 
+           (char-ci-loop x x* char<? 'char-ci<?)
+           (error 'char-ci<? "not a char" x))]))
 
   (define char-ci<=? 
     (case-lambda 
@@ -153,11 +173,14 @@
            (or (eq? x y)
                (if (char? y)
                    ($fx<= ($fold x) ($fold y))
-                   (error 'char-ci<=? "~s is not a char" y)))
-           (error 'char-ci<=? "~s is not a char" x))]
+                   (error 'char-ci<=? "not a char" y)))
+           (error 'char-ci<=? "not a char" x))]
       [(x)
-       (or (char? x) (error 'char-ci<=? "~s is not a char" x))]
-      [ls (error 'char-ci<=? "not supported ~s" ls)]))
+       (or (char? x) (error 'char-ci<=? "not a char" x))]
+      [(x . x*) 
+       (if (char? x) 
+           (char-ci-loop x x* char<=? 'char-ci<=?)
+           (error 'char-ci<=? "not a char" x))]))
 
   (define char-ci>? 
     (case-lambda 
@@ -166,11 +189,14 @@
            (or (eq? x y)
                (if (char? y)
                    ($fx> ($fold x) ($fold y))
-                   (error 'char-ci>? "~s is not a char" y)))
-           (error 'char-ci>? "~s is not a char" x))]
+                   (error 'char-ci>? "not a char" y)))
+           (error 'char-ci>? "not a char" x))]
       [(x)
-       (or (char? x) (error 'char-ci>? "~s is not a char" x))]
-      [ls (error 'char-ci>? "not supported ~s" ls)]))
+       (or (char? x) (error 'char-ci>? "not a char" x))]
+      [(x . x*) 
+       (if (char? x) 
+           (char-ci-loop x x* char>? 'char-ci>?)
+           (error 'char-ci>? "not a char" x))]))
   
   (define char-ci>=? 
     (case-lambda 
@@ -179,11 +205,14 @@
            (or (eq? x y)
                (if (char? y)
                    ($fx>= ($fold x) ($fold y))
-                   (error 'char-ci>=? "~s is not a char" y)))
-           (error 'char-ci>=? "~s is not a char" x))]
+                   (error 'char-ci>=? "not a char" y)))
+           (error 'char-ci>=? "not a char" x))]
       [(x)
-       (or (char? x) (error 'char-ci>=? "~s is not a char" x))]
-      [ls (error 'char-ci>=? "not supported ~s" ls)]))
+       (or (char? x) (error 'char-ci>=? "not a char" x))]
+      [(x . x*) 
+       (if (char? x) 
+           (char-ci-loop x x* char>=? 'char-ci>=?)
+           (error 'char-ci>=? "not a char" x))]))
                
   (define ($string-foldcase str)
     (let f ([str str] [i 0] [n (string-length str)] [p (open-output-string)])
@@ -207,7 +236,7 @@
   (define (string-foldcase str)
     (if (string? str)
         ($string-foldcase str)
-        (error 'string-foldcase "~s is not a string" str)))
+        (error 'string-foldcase "not a string" str)))
 
   ;;; FIXME: case-insensitive comparison procedures are slow.
 
@@ -218,8 +247,8 @@
          (if (string? s1)
              (if (string? s2) 
                  (cmp ($string-foldcase s1) ($string-foldcase s2))
-                 (error who "~s is not a string" s2))
-             (error who "~s is not a string" s1))]
+                 (error who "not a string" s2))
+             (error who "not a string" s1))]
         [(s1 . s*) 
          (if (string? s1) 
              (let ([s1 ($string-foldcase s1)])
@@ -238,10 +267,10 @@
                                     [(string? (car s*)) 
                                      (f (cdr s*))]
                                     [else 
-                                     (error who "~s is not a string" 
+                                     (error who "not a string" 
                                        (car s*))]))))
-                          (error who "~s is not a string" s2)))])))
-             (error who "~s is not a string" s1))])))
+                          (error who "not a string" s2)))])))
+             (error who "not a string" s1))])))
 
 
   (define string-ci=?  (string-ci-cmp 'string-ci=? string=?))
diff --git a/scheme/ikarus.vectors.ss b/scheme/ikarus.vectors.ss
index 343fcc8..f6e74d0 100644
--- a/scheme/ikarus.vectors.ss
+++ b/scheme/ikarus.vectors.ss
@@ -16,7 +16,7 @@
   (define vector-length
     (lambda (x)
       (unless (vector? x) 
-        (error 'vector-length "~s is not a vector" x))
+        (error 'vector-length "not a vector" x))
       ($vector-length x)))
 
   (module (make-vector)
@@ -32,7 +32,7 @@
         [(n) (make-vector n (void))]
         [(n fill)
          (unless (and (fixnum? n) ($fx>= n 0))
-           (error 'make-vector "~s is not a valid length" n))
+           (error 'make-vector "not a valid length" n))
          (fill! ($make-vector n) 0 n fill)])))
 
 
@@ -59,23 +59,23 @@
   (define vector-ref 
     (lambda (v i)
       (unless (vector? v)
-        (error 'vector-ref "~s is not a vector" v))
+        (error 'vector-ref "not a vector" v))
       (unless (fixnum? i)
-        (error 'vector-ref "~s is not a valid index" i))
+        (error 'vector-ref "not a valid index" i))
       (unless (and ($fx< i ($vector-length v))
                    ($fx<= 0 i))
-        (error 'vector-ref "index ~s is out of range for ~s" i v))
+        (error 'vector-ref "index is out of range" i v))
       ($vector-ref v i)))
   
   (define vector-set! 
     (lambda (v i c) 
       (unless (vector? v) 
-        (error 'vector-set! "~s is not a vector" v))
+        (error 'vector-set! "not a vector" v))
       (unless (fixnum? i)
-        (error 'vector-set! "~s is not a valid index" i))
+        (error 'vector-set! "not a valid index" i))
       (unless (and ($fx< i ($vector-length v))
                    ($fx<= 0 i))
-        (error 'vector-set! "index ~s is out of range for ~s" i v))
+        (error 'vector-set! "index is out of range" i v))
       ($vector-set! v i c)))
 
   (define vector->list
@@ -91,7 +91,7 @@
             (if ($fxzero? n)
                 '()
                 (f v ($fxsub1 n) '())))
-          (error 'vector->list "~s is not a vector" v))))
+          (error 'vector->list "not a vector" v))))
 
   (define list->vector
     (letrec ([race
@@ -101,13 +101,13 @@
                       (if (pair? h)
                           (if (not (eq? h t))
                               (race ($cdr h) ($cdr t) ls ($fx+ n 2))
-                              (error 'list->vector "circular list ~s" ls))
+                              (error 'list->vector "circular list" ls))
                           (if (null? h)
                               ($fx+ n 1)
-                              (error 'list->vector "~s is not a proper list" ls))))
+                              (error 'list->vector "not a proper list" ls))))
                    (if (null? h)
                        n
-                       (error 'list->vector "~s is not a proper list" ls))))]
+                       (error 'list->vector "not a proper list" ls))))]
               [fill
                (lambda (v i ls)
                  (cond
@@ -137,9 +137,9 @@
       (case-lambda
         [(p v) 
          (unless (procedure? p) 
-           (error who "~s is not a procedure" p))
+           (error who "not a procedure" p))
          (unless (vector? v) 
-           (error who "~s is not a vector" v))
+           (error who "not a vector" v))
          (let f ([p p] [v v] [i 0] [n (vector-length v)] [ac '()])
            (cond
              [($fx= i n) (ls->vec ac n)]
@@ -147,14 +147,14 @@
               (f p v ($fxadd1 i) n (cons (p (vector-ref v i)) ac))]))]
         [(p v0 v1) 
          (unless (procedure? p) 
-           (error who "~s is not a procedure" p))
+           (error who "not a procedure" p))
          (unless (vector? v0) 
-           (error who "~s is not a vector" v0))
+           (error who "not a vector" v0))
          (unless (vector? v1) 
-           (error who "~s is not a vector" v1))
+           (error who "not a vector" v1))
          (let ([n (vector-length v0)])
            (unless ($fx= n ($vector-length v1))
-             (error who "length mismatch between ~s and ~s" v0 v1))
+             (error who "length mismatch" v0 v1))
            (let f ([p p] [v0 v0] [v1 v1] [i 0] [n n] [ac '()])
              (cond
                [($fx= i n) (ls->vec ac n)]
@@ -163,19 +163,19 @@
                    (cons (p ($vector-ref v0 i) ($vector-ref v1 i)) ac))])))]
         [(p v0 v1 . v*) 
          (unless (procedure? p) 
-           (error who "~s is not a procedure" p))
+           (error who "not a procedure" p))
          (unless (vector? v0) 
-           (error who "~s is not a vector" v0))
+           (error who "not a vector" v0))
          (unless (vector? v1) 
-           (error who "~s is not a vector" v1))
+           (error who "not a vector" v1))
          (let ([n (vector-length v0)])
            (unless ($fx= n ($vector-length v1))
-             (error who "length mismatch between ~s and ~s" v0 v1))
+             (error who "length mismatch" v0 v1))
            (let f ([v* v*] [n n])
              (unless (null? v*) 
                (let ([a ($car v*)])
                  (unless (vector? a) 
-                   (error who "~s is not a vector" a))
+                   (error who "not a vector" a))
                  (unless ($fx= ($vector-length a) n) 
                    (error who "length mismatch")))
                (f ($cdr v*) n)))
@@ -200,9 +200,9 @@
       (case-lambda
         [(p v) 
          (unless (procedure? p) 
-           (error who "~s is not a procedure" p))
+           (error who "not a procedure" p))
          (unless (vector? v) 
-           (error who "~s is not a vector" v))
+           (error who "not a vector" v))
          (let f ([p p] [v v] [i 0] [n (vector-length v)])
            (cond
              [($fx= i n) (void)]
@@ -211,14 +211,14 @@
               (f p v ($fxadd1 i) n)]))]
         [(p v0 v1) 
          (unless (procedure? p) 
-           (error who "~s is not a procedure" p))
+           (error who "not a procedure" p))
          (unless (vector? v0) 
-           (error who "~s is not a vector" v0))
+           (error who "not a vector" v0))
          (unless (vector? v1) 
-           (error who "~s is not a vector" v1))
+           (error who "not a vector" v1))
          (let ([n (vector-length v0)])
            (unless ($fx= n ($vector-length v1))
-             (error who "length mismatch between ~s and ~s" v0 v1))
+             (error who "length mismatch" v0 v1))
            (let f ([p p] [v0 v0] [v1 v1] [i 0] [n n])
              (cond
                [($fx= i n) (void)]
@@ -227,19 +227,19 @@
                 (f p v0 v1 ($fxadd1 i) n)])))]
         [(p v0 v1 . v*) 
          (unless (procedure? p) 
-           (error who "~s is not a procedure" p))
+           (error who "not a procedure" p))
          (unless (vector? v0) 
-           (error who "~s is not a vector" v0))
+           (error who "not a vector" v0))
          (unless (vector? v1) 
-           (error who "~s is not a vector" v1))
+           (error who "not a vector" v1))
          (let ([n (vector-length v0)])
            (unless ($fx= n ($vector-length v1))
-             (error who "length mismatch between ~s and ~s" v0 v1))
+             (error who "length mismatch" v0 v1))
            (let f ([v* v*] [n n])
              (unless (null? v*) 
                (let ([a ($car v*)])
                  (unless (vector? a) 
-                   (error who "~s is not a vector" a))
+                   (error who "not a vector" a))
                  (unless ($fx= ($vector-length a) n) 
                    (error who "length mismatch")))
                (f ($cdr v*) n)))
@@ -257,7 +257,7 @@
 
   (define (vector-fill! v fill)
     (unless (vector? v) 
-      (error 'vector-fill! "~s is not a vector" v))
+      (error 'vector-fill! "not a vector" v))
     (let f ([v v] [i 0] [n ($vector-length v)] [fill fill])
       (unless ($fx= i n) 
         ($vector-set! v i fill)
diff --git a/scheme/ikarus.writer.ss b/scheme/ikarus.writer.ss
index f8ac89d..a2d226a 100644
--- a/scheme/ikarus.writer.ss
+++ b/scheme/ikarus.writer.ss
@@ -1,6 +1,6 @@
 
 (library (ikarus writer)
-  (export write display format printf print-error print-unicode print-graph)
+  (export write display format printf fprintf print-error print-unicode print-graph)
   (import 
     (rnrs hashtables)
     (ikarus system $chars)
@@ -12,7 +12,8 @@
     (ikarus system $bytevectors)
     (ikarus system $transcoders)
     (only (ikarus unicode-data) unicode-printable-char?) 
-    (except (ikarus) write display format printf print-error print-unicode print-graph))
+    (except (ikarus) 
+      write display format printf fprintf print-error print-unicode print-graph))
 
   (define print-unicode
     (make-parameter #t))
@@ -654,7 +655,7 @@
               [($char= c #\~)
                (let ([i (fxadd1 i)])
                  (when (fx= i (string-length fmt))
-                   (error who "invalid ~~ at end of format string ~s" fmt))
+                   (error who "invalid ~ at end of format string" fmt))
                  (let ([c (string-ref fmt i)])
                   (cond
                     [($char= c #\~) 
@@ -674,7 +675,7 @@
                      (write-to-port (car args) p)
                      (f (fxadd1 i) (cdr args))]
                     [else
-                     (error who "invalid sequence ~~~a" c)])))]
+                     (error who "invalid sequence character after ~" c)])))]
               [else 
                (write-char c p)
                (f (fxadd1 i) args)]))))
@@ -683,15 +684,15 @@
   (define fprintf
     (lambda (port fmt . args)
       (unless (output-port? port) 
-        (error 'fprintf "~s is not an output port" port))
+        (error 'fprintf "not an output port" port))
       (unless (string? fmt)
-        (error 'fprintf "~s is not a string" fmt))
+        (error 'fprintf "not a string" fmt))
       (formatter 'fprintf port fmt args)))
 
   (define display-error
     (lambda (errname who fmt args)
       (unless (string? fmt)
-        (error 'print-error "~s is not a string" fmt))
+        (error 'print-error "not a string" fmt))
       (let ([p (standard-error-port)])
         (if who
             (fprintf p "~a in ~a: " errname who)
@@ -703,7 +704,7 @@
   (define format
     (lambda (fmt . args)
       (unless (string? fmt)
-        (error 'format "~s is not a string" fmt))
+        (error 'format "not a string" fmt))
       (let ([p (open-output-string)])
         (formatter 'format p fmt args)
         (get-output-string p))))
@@ -711,7 +712,7 @@
   (define printf 
     (lambda (fmt . args)
       (unless (string? fmt)
-        (error 'printf "~s is not a string" fmt))
+        (error 'printf "not a string" fmt))
       (formatter 'printf (current-output-port) fmt args)))
   
   (define write 
@@ -719,7 +720,7 @@
       [(x) (write-to-port x (current-output-port))]
       [(x p)
        (unless (output-port? p) 
-         (error 'write "~s is not an output port" p))
+         (error 'write "not an output port" p))
        (write-to-port x p)]))
 
   (define display 
@@ -727,7 +728,7 @@
       [(x) (display-to-port x (current-output-port))]
       [(x p)
        (unless (output-port? p) 
-         (error 'display "~s is not an output port" p))
+         (error 'display "not an output port" p))
        (display-to-port x p)]))
 
   (define print-error 
diff --git a/scheme/makefile.ss b/scheme/makefile.ss
index c52f6e0..b2ee77e 100755
--- a/scheme/makefile.ss
+++ b/scheme/makefile.ss
@@ -1332,7 +1332,7 @@
     (for-each 
       (lambda (x) 
         (unless (assq x library-legend)
-          (error 'verify "~s is not in the libraries list" x)))
+          (error 'verify "not in the libraries list" x)))
       (cdr x)))
   (for-each f identifier->library-map))
 
@@ -1373,12 +1373,12 @@
         (when (procedure-identifier? x)
           (cond
             [(assq x (export-subst))
-             (error who "ambiguous export of ~s" x)]
+             (error who "ambiguous export" x)]
             [(assq1 x subst) =>
              ;;; primitive defined (exported) within the compiled libraries
              (lambda (p)
                (unless (pair? p) 
-                 (error who "~s exports of ~s" p x))
+                 (error who "invalid exports" p x))
                (let ([label (cdr p)])
                  (cond
                    [(assq label env) =>
@@ -1390,9 +1390,8 @@
                            (export-env   (cons label (cons 'core-prim x)))
                            (export-primlocs (cons x (cdr binding)))]
                           [else 
-                           (error #f "invalid binding ~s for ~s" p x)])))]
-                   [else (error #f "cannot find binding for ~s ~s" x
-                                label)])))]
+                           (error #f "invalid binding for identifier" p x)])))]
+                   [else (error #f "cannot find binding" x label)])))]
             [else 
              ;;; core primitive with no backing definition, assumed to
              ;;; be defined in other strata of the system
@@ -1486,7 +1485,7 @@
                       [,args
                        ((primitive error)
                          'apply 
-                         '"~s is not a procedure"
+                         '"not a procedure"
                          ((primitive $symbol-value) ,sym))]))))])))
     `([$init-symbol-value! . ,label])
     `([,label . (global . ,loc)])))
@@ -1533,7 +1532,7 @@
             (cond
               [(assq x locs) => cdr]
               [else 
-               (error 'bootstrap "no location for ~s" x)])))
+               (error 'bootstrap "no location for primitive" x)])))
         (let ([p (open-output-file "ikarus.boot" 'replace)])
           (for-each 
             (lambda (x) 
diff --git a/scheme/pass-specify-rep.ss b/scheme/pass-specify-rep.ss
index 417fdf1..2ec5d61 100644
--- a/scheme/pass-specify-rep.ss
+++ b/scheme/pass-specify-rep.ss
@@ -23,7 +23,7 @@
     (and (getprop x cookie) #t))
   (define (get-primop x)
     (or (getprop x cookie)
-        (error 'getprimop "~s is not a primitive" x)))
+        (error 'getprimop "not a primitive" x)))
   (define (set-primop! x v)
     (putprop x cookie v))
   )
@@ -53,7 +53,7 @@
       [(not (PH-interruptable? p))
        (parameterize ([interrupt-handler 
                        (lambda ()
-                         (error 'cogen "~s ~s is uninterruptable in ~s" 
+                         (error 'cogen "uninterruptable" 
                                 x args ctxt))])
           (k))]
       [else
@@ -85,7 +85,7 @@
                       [else #f])
                      (prm '!= (make-no-interrupt-call x args) (K bool-f))
                      (make-shortcut body h)))]
-             [else (error 'with-interrupt-handler "invalid context ~s" ctxt)])))]))
+             [else (error 'with-interrupt-handler "invalid context" ctxt)])))]))
   (define-syntax with-tmp
     (lambda (x)
       (syntax-case x ()
@@ -151,7 +151,7 @@
                     [(PH-e-handled? p)
                      (let ([e (apply (PH-e-handler p) args)])
                        (if (interrupt? e) e (make-seq e (K #t))))]
-                    [else (error 'cogen-primop "~s is not handled" x)])]
+                    [else (error 'cogen-primop "not handled" x)])]
                  [(V) 
                   (cond
                     [(PH-v-handled? p) 
@@ -164,7 +164,7 @@
                     [(PH-e-handled? p)
                      (let ([e (apply (PH-e-handler p) args)])
                        (if (interrupt? e) e (make-seq e (K void-object))))]
-                    [else (error 'cogen-primop "~s is not handled" x)])]
+                    [else (error 'cogen-primop "not handled" x)])]
                  [(E) 
                   (cond
                     [(PH-e-handled? p) 
@@ -179,9 +179,9 @@
                        (if (interrupt? e)
                            e
                            (with-tmp ([t e]) (prm 'nop))))]
-                    [else (error 'cogen-primop "~s is not handled" x)])]
+                    [else (error 'cogen-primop "not handled" x)])]
                  [else 
-                  (error 'cogen-primop "invalid context ~s" ctxt)])))))))
+                  (error 'cogen-primop "invalid context" ctxt)])))))))
   
   (define-syntax define-primop
     (lambda (x)
@@ -350,7 +350,7 @@
        (make-funcall (Function rator) (map V arg*))]
       [(jmpcall label rator arg*)
        (make-jmpcall label (V rator) (map V arg*))]
-      [else (error 'cogen-V "invalid value expr ~s" x)])) 
+      [else (error 'cogen-V "invalid value expr" x)])) 
 
   (define (P x)
     (struct-case x
@@ -372,7 +372,7 @@
       [(funcall) (prm '!= (V x) (V (K #f)))]
       [(jmpcall) (prm '!= (V x) (V (K #f)))]
       [(forcall) (prm '!= (V x) (V (K #f)))]
-      [else (error 'cogen-P "invalid pred expr ~s" x)])) 
+      [else (error 'cogen-P "invalid pred expr" x)])) 
   
   (define (E x)
     (struct-case x
@@ -397,7 +397,7 @@
        (make-funcall (Function rator) (map V arg*))]
       [(jmpcall label rator arg*)
        (make-jmpcall label (V rator) (map V arg*))]
-      [else (error 'cogen-E "invalid effect expr ~s" x)]))
+      [else (error 'cogen-E "invalid effect expr" x)]))
 
   (define (Function x)
     (define (nonproc x)
@@ -410,7 +410,7 @@
               (prm 'interrupt))
             x)
           (V (make-funcall (make-primref 'error)
-               (list (K 'apply) (K "~s is not a procedure") x))))))
+               (list (K 'apply) (K "not a procedure") x))))))
     (struct-case x
        [(primcall op args)
         (cond
@@ -452,13 +452,13 @@
     (struct-case x
       [(var) x]
       [(constant i) (constant-rep x)]
-      [else (error 'cogen-T "invalid ~s" (unparse x))]))
+      [else (error 'cogen-T "invalid" (unparse x))]))
 
   (define (ClambdaCase x)
     (struct-case x
       [(clambda-case info body)
        (make-clambda-case info (V body))]
-      [else (error 'specify-rep "invalid clambda-case ~s" x)]))
+      [else (error 'specify-rep "invalid clambda-case" x)]))
   ;;;
   (define (Clambda x)
     (struct-case x
@@ -466,7 +466,7 @@
        (make-clambda label 
           (map ClambdaCase case*)
           free* name)]
-      [else (error 'specify-rep "invalid clambda ~s" x)]))
+      [else (error 'specify-rep "invalid clambda" x)]))
   ;;;
   (define (Program x)
     (struct-case x 
@@ -474,7 +474,7 @@
        (let ([code* (map Clambda code*)]
              [body (V body)])
          (make-codes code* body))]
-      [else (error 'specify-rep "invalid program ~s" x)]))
+      [else (error 'specify-rep "invalid program" x)]))
 
   (define (specify-representation x)
     (let ([x (Program x)])
diff --git a/scheme/psyntax.expander.ss b/scheme/psyntax.expander.ss
index 150ef50..cea0f41 100644
--- a/scheme/psyntax.expander.ss
+++ b/scheme/psyntax.expander.ss
@@ -74,7 +74,7 @@
       (cond
         ((symbol? sym) (gensym sym))
         ((stx? sym) (gen-lexical (id->sym sym)))
-        (else (error 'gen-lexical "BUG: invalid arg ~s" sym)))))
+        (else (error 'gen-lexical "BUG: invalid arg" sym)))))
   
   ;;; gen-global is used to generate global names (e.g. locations
   ;;; for library exports).  We use gen-lexical since it works just 
@@ -115,7 +115,7 @@
                     (same-marks? mark* (car mark**)))
                (find sym mark* (cdr sym*) (cdr mark**)))))
     (when (rib-sealed/freq rib)
-      (error 'extend-rib! "rib ~s is sealed" rib))
+      (error 'extend-rib! "rib is sealed" rib))
     (let ((sym (id->sym id)) (mark* (stx-mark* id)))
       (let ((sym* (rib-sym* rib)))
         (when (and (memq sym (rib-sym* rib))
@@ -339,7 +339,7 @@
                (m* (stx-mark* x)) (s* (stx-subst* x)))
            (map (lambda (x) (mkstx x m* s*)) ls)))
         ((vector? x) (vector->list x))
-        (else (error 'syntax-vector->list "not a syntax vector ~s" x)))))
+        (else (error 'syntax-vector->list "not a syntax vector" x)))))
   (define syntax-pair?
     (lambda (x) (syntax-kind? x pair?)))
   (define syntax-vector?
@@ -356,21 +356,21 @@
           (mkstx (syntax-car (stx-expr x)) (stx-mark* x) (stx-subst* x))
           (if (pair? x)
               (car x)
-              (error 'syntax-car "~s is not a pair" x)))))
+              (error 'syntax-car "not a pair" x)))))
   (define syntax->list
     (lambda (x)
       (if (syntax-pair? x)
           (cons (syntax-car x) (syntax->list (syntax-cdr x)))
           (if (syntax-null? x)
               '()
-              (error 'syntax->list "invalid ~s" x)))))
+              (error 'syntax->list "invalid argument" x)))))
   (define syntax-cdr
     (lambda (x)
       (if (stx? x)
           (mkstx (syntax-cdr (stx-expr x)) (stx-mark* x) (stx-subst* x))
           (if (pair? x)
               (cdr x)
-              (error 'syntax-cdr "~s is not a pair" x)))))
+              (error 'syntax-cdr "not a pair" x)))))
   (define id?
     (lambda (x) (syntax-kind? x symbol?)))
   
@@ -380,7 +380,7 @@
           (id->sym (stx-expr x))
           (if (symbol? x)
               x
-              (error 'id->sym "~s is not an id" x)))))
+              (error 'id->sym "not an id" x)))))
 
   ;;; Two lists of marks are considered the same if they have the 
   ;;; same length and the corresponding marks on each are eq?.
@@ -568,8 +568,8 @@
     (lambda (x)
       (syntax-case x ()
         ((_ stx)
-         (syntax (error 'expander "invalid syntax ~s" (stx->datum stx))))
-        ((_ stx msg) (syntax (error 'expander "~a ~s" msg (strip stx '())))))))
+         (syntax (error 'expander "invalid syntax" (stx->datum stx))))
+        ((_ stx msg) (syntax (error 'expander msg (strip stx '())))))))
   
   ;;; when the rhs of a syntax definition is evaluated, it should be
   ;;; either a procedure, an identifier-syntax transformer or an
@@ -587,7 +587,7 @@
         ((and (pair? x) (eq? (car x) 'macro!) (procedure? (cdr x)))
          (cons* 'local-macro! (cdr x) src))
         ((and (pair? x) (eq? (car x) '$rtd)) x)
-        (else (error 'expand "invalid transformer ~s" x)))))
+        (else (error 'expand "invalid transformer" x)))))
   
   ;;; r6rs's make-variable-transformer:
   (define make-variable-transformer
@@ -595,7 +595,7 @@
       (if (procedure? x)
           (cons 'macro! x)
           (error 'make-variable-transformer
-                 "~s is not a procedure" x))))
+                 "not a procedure" x))))
 
   ;;; make-eval-transformer takes an expanded expression, 
   ;;; evaluates it and returns a proper syntactic binding
@@ -1026,7 +1026,7 @@
                          (if (procedure? v)
                              (make-traced-procedure ',who v)
                              (error 'trace-define
-                                "~s is not a procedure" v)))))
+                                "not a procedure" v)))))
              (stx-error stx "invalid formals"))))))
   
   (define time-macro
@@ -1046,7 +1046,7 @@
       (syntax-match stx ()
         ((_ expr)
          (bless `(unless ,expr
-                   (error 'assert "~s failed" ',expr)))))))
+                   (error 'assert "assertion failed" ',expr)))))))
   
   (define endianness-macro
     (lambda (stx)
@@ -1398,7 +1398,7 @@
                                  (if ($struct/rtd? x ',rtd)
                                      ($struct-ref x ,i)
                                      (error ',getter
-                                            "~s is not a struct of type ~s"
+                                            "not a struct of required type"
                                             x ',rtd)))))
                          getters i*)
                   ,@(map (lambda (setter i)
@@ -1407,7 +1407,7 @@
                                  (if ($struct/rtd? x ',rtd)
                                      ($struct-set! x ,i v)
                                      (error ',setter
-                                            "~s is not a struct of type ~s"
+                                            "not a struct of required type"
                                             x ',rtd)))))
                          setters i*)))))))
       (lambda (stx)
@@ -2110,7 +2110,7 @@
         ((type-descriptor)        type-descriptor-transformer)
         ((record-type-descriptor) record-type-descriptor-transformer)
         ((record-constructor-descriptor) record-constructor-descriptor-transformer)
-        (else (error 'macro-transformer "cannot find ~s" name)))))
+        (else (error 'macro-transformer "cannot find transformer" name)))))
   
   (define file-options-macro
     (lambda (x)
@@ -2168,8 +2168,8 @@
              fields mutable immutable parent protocol
              sealed opaque nongenerative parent-rtd)
             incorrect-usage-macro)
-           (else (error 'macro-transformer "invalid macro ~s" x))))
-        (else (error 'core-macro-transformer "invalid macro ~s" x)))))
+           (else (error 'macro-transformer "invalid macro" x))))
+        (else (error 'core-macro-transformer "invalid macro" x)))))
   
   (define (local-macro-transformer x)
     (car x))
@@ -2194,7 +2194,7 @@
         (let ((transformer
                (cond
                  ((procedure? x) x)
-                 (else (error 'chi-global-macro "~s is not a procedure")))))
+                 (else (error 'chi-global-macro "not a procedure")))))
           (let ((s (transformer (add-mark anti-mark e))))
             (add-mark (gen-mark) s))))))
   
@@ -2272,7 +2272,7 @@
           ((define define-syntax module import)
            (stx-error e "invalid expression"))
           (else
-           ;(error 'chi-expr "invalid type ~s for ~s" type (strip e '()))
+           ;(error 'chi-expr "invalid type " type (strip e '()))
            (stx-error e "invalid expression"))))))
 
   (define chi-set!
@@ -2350,7 +2350,7 @@
            (build-sequence no-source
              (list (chi-expr expr r mr)
                    (build-void)))))
-        (else (error 'chi-rhs "invalid rhs ~s" rhs)))))
+        (else (error 'chi-rhs "invalid rhs" rhs)))))
 
   (define chi-rhs*
     (lambda (rhs* r mr)
@@ -2586,7 +2586,7 @@
                         (set-global-macro-binding! (id->sym id) loc b)
                         (chi-top* (cdr e*) init*))))))
                ((let-syntax letrec-syntax) 
-                (error 'chi-top* "~s is not supported yet at top level" type))
+                (error 'chi-top* "not supported yet at top level" type))
                ((begin)
                 (syntax-match e ()
                   ((_ x* ...)
@@ -2622,7 +2622,7 @@
         ((null? exp*)
          (let ((id* (map (lambda (x) (mkstx x top-mark* '())) ext*)))
            (unless (valid-bound-ids? id*)
-             (error 'expander "invalid exports of ~s" (find-dups id*))))
+             (error 'expander "invalid exports" (find-dups id*))))
          (values int* ext*))
         (else
          (syntax-match (car exp*) ()
@@ -2630,11 +2630,11 @@
             (begin
               (unless (and (eq? rename 'rename) (for-all symbol? i*)
                            (for-all symbol? e*))
-                (error 'expander "invalid export specifier ~s" (car exp*)))
+                (error 'expander "invalid export specifier" (car exp*)))
               (f (cdr exp*) (append i* int*) (append e* ext*))))
            (ie
             (begin
-              (unless (symbol? ie) (error 'expander "invalid export ~s" ie))
+              (unless (symbol? ie) (error 'expander "invalid export" ie))
               (f (cdr exp*) (cons ie int*) (cons ie ext*)))))))))
 
   ;;; given a library name, like (foo bar (1 2 3)), 
@@ -2684,7 +2684,7 @@
                  ((eq? (cdr x) label) subst)
                  (else
                   (error 'import
-                     "two imports of ~s with different bindings"
+                     "two imports with different bindings"
                      name)))))
             (else
              (cons a subst)))))
@@ -2697,7 +2697,7 @@
       (define (exclude sym subst)
         (cond
           ((null? subst)
-           (error 'import "cannot rename unbound identifier ~s" sym))
+           (error 'import "cannot rename unbound identifier" sym))
           ((eq? sym (caar subst))
            (values (cdar subst) (cdr subst)))
           (else
@@ -2714,7 +2714,7 @@
       (map (lambda (x)
              (cond
                ((assq x subst) => cdr)
-               (else (error 'import "cannot find identifier ~s" x))))
+               (else (error 'import "cannot find identifier" x))))
            sym*))
     (define (rem* sym* subst)
       (let f ((subst subst))
@@ -2761,13 +2761,15 @@
         ((library name) (eq? library 'library)
          (let ((lib (find-library-by-name name)))
            (unless lib
-             (error 'import "cannot find library satisfying ~s" name))
+             (error 'import 
+                "cannot find library satisfying required name"
+                name))
            (imp-collector lib)
            (library-subst lib)))
         ((x x* ...)
          (not (memq x '(rename except only prefix library)))
          (get-import `(library (,x . ,x*))))
-        (spec (error 'import "invalid import spec ~s" spec))))
+        (spec (error 'import "invalid import spec" spec))))
     (let f ((imp* imp*) (subst '()))
       (cond
         ((null? imp*) (values subst (imp-collector)))
@@ -2803,7 +2805,7 @@
         (error 'inv-collector "not initialized"))
       (lambda (x)
         (unless (procedure? x)
-          (error 'inv-collector "~s is not a procedure" x))
+          (error 'inv-collector "not a procedure" x))
         x)))
   
   (define vis-collector
@@ -2812,7 +2814,7 @@
         (error 'vis-collector "not initialized"))
       (lambda (x)
         (unless (procedure? x)
-          (error 'vis-collector "~s is not a procedure" x))
+          (error 'vis-collector "not a procedure" x))
         x)))
   
   (define chi-library-internal
@@ -2901,11 +2903,11 @@
   ;;; constructed simply using the corresponding libraries.
   (define (null-environment n)
     (unless (eqv? n 5)
-      (error 'null-environment "~s is not 5" n))
+      (error 'null-environment "not 5" n))
     (environment '(psyntax null-environment-5)))
   (define (scheme-report-environment n)
     (unless (eqv? n 5)
-      (error 'scheme-report-environment "~s is not 5" n))
+      (error 'scheme-report-environment "not 5" n))
     (environment '(psyntax scheme-report-environment-5)))
 
   ;;; The expand procedure is the interface to the internal expression
@@ -2915,7 +2917,7 @@
   (define expand
     (lambda (x env)
       (unless (env? env)
-        (error 'expand "~s is not an environment" env))
+        (error 'expand "not an environment" env))
       (let ((subst (env-subst env)))
         (let ((rib (make-top-rib subst)))
           (let ((x (mkstx x top-mark* (list rib)))
@@ -2934,7 +2936,7 @@
   (define eval
     (lambda (x env)
       (unless (env? env)
-        (error 'eval "~s is not an environment" env))
+        (error 'eval "not an environment" env))
       (let-values (((x invoke-req*) (expand x env)))
         (for-each invoke-library invoke-req*)
         (eval-core (expanded->core x)))))
@@ -3035,7 +3037,7 @@
                      (cons (cons loc (binding-value b)) macro*))))
                (($rtd $module) (f (cdr r) (cons x env) global* macro*))
                (else
-                (error 'expander "BUG: do not know how to export ~s ~s"
+                (error 'expander "BUG: do not know how to export"
                        (binding-type b) (binding-value b))))))))))
   
   (define generate-temporaries
@@ -3044,31 +3046,30 @@
         ((ls ...)
          (map (lambda (x) (make-stx (gensym 't) top-mark* '())) ls))
         (_ 
-         (error 'generate-temporaries "~s is not a list")))))
+         (error 'generate-temporaries "not a list")))))
   
   (define free-identifier=?
     (lambda (x y)
       (if (id? x)
           (if (id? y)
               (free-id=? x y)
-              (error 'free-identifier=? "~s is not an identifier" y))
-          (error 'free-identifier=? "~s is not an identifier" x))))
+              (error 'free-identifier=? "not an identifier" y))
+          (error 'free-identifier=? "not an identifier" x))))
   
   (define bound-identifier=?
     (lambda (x y)
       (if (id? x)
           (if (id? y)
               (bound-id=? x y)
-              (error 'bound-identifier=? "~s is not an identifier" y))
-          (error 'bound-identifier=? "~s is not an identifier" x))))
+              (error 'bound-identifier=? "not an identifier" y))
+          (error 'bound-identifier=? "not an identifier" x))))
   
   (define syntax-error
     (lambda (x . args)
       (unless (for-all string? args)
-        (error 'syntax-error "invalid argument ~s" args))
-      (if (null? args)
-          (error 'expander "invalid syntax ~s" (stx->datum x))
-          (error 'expander "~s ~a" (stx->datum x) (apply string-append args)))))
+        (error 'syntax-error "invalid argument" args))
+      (error 'expander "invalid syntax"
+          (stx->datum x) (apply string-append args))))
   
   (define identifier? (lambda (x) (id? x)))
   
@@ -3076,7 +3077,7 @@
     (lambda (id datum)
       (if (id? id)
           (datum->stx id datum)
-          (error 'datum->syntax "~s is not an identifier" id))))
+          (error 'datum->syntax "not an identifier" id))))
   
   (define syntax->datum
     (lambda (x) (stx->datum x)))
diff --git a/scheme/psyntax.library-manager.ss b/scheme/psyntax.library-manager.ss
index 53aecb4..5545408 100644
--- a/scheme/psyntax.library-manager.ss
+++ b/scheme/psyntax.library-manager.ss
@@ -43,7 +43,7 @@
     (make-parameter (make-collection)
       (lambda (x)
         (unless (procedure? x)
-          (error 'current-library-collection "~s is not a procedure" x))
+          (error 'current-library-collection "not a procedure" x))
         x)))
 
   (define-record library 
@@ -74,7 +74,7 @@
         (if (and (list? x) (for-all string? x))
             ;(map values x)
             (map (lambda (x) x) x)
-            (error 'library-path "~s is not a list of strings" x)))))
+            (error 'library-path "not a list of strings" x)))))
   
   (define (library-name->file-name x) 
     (let-values (((p extract) (open-string-output-port)))
@@ -122,7 +122,7 @@
       (lambda (f)
         (if (procedure? f)
             f
-            (error 'file-locator "~s is not a procedure" f)))))
+            (error 'file-locator "not a procedure" f)))))
 
   (define library-locator
     (make-parameter
@@ -134,7 +134,7 @@
         (if (procedure? f)
             f
             (error 'library-locator 
-                   "~s is not a procedure" f)))))
+                   "not a procedure" f)))))
 
   (define current-library-expander
     (make-parameter
@@ -144,24 +144,26 @@
         (if (procedure? f)
             f
             (error 'library-expander 
-                   "~s is not a procedure" f)))))
+                   "not a procedure" f)))))
 
   (define external-pending-libraries 
     (make-parameter '()))
 
   (define (find-external-library name)
     (when (member name (external-pending-libraries))
-      (error #f "circular attempt to import library ~s detected"
+      (error #f "circular attempt to import library was detected"
              name))
     (parameterize ((external-pending-libraries
                     (cons name (external-pending-libraries))))
       (let ((lib-expr ((library-locator) name)))
         (unless lib-expr 
-          (error #f "cannot find library ~s" name))
+          (error #f "cannot find library" name))
         ((current-library-expander) lib-expr)
         (or (find-library-by
               (lambda (x) (equal? (library-name x) name)))
-            (error #f "handling external library of ~s did not yield the currect library" name)))))
+            (error #f
+              "handling external library did not yield the currect library"
+               name)))))
           
   (define (find-library-by-name name)
     (or (find-library-by
@@ -177,7 +179,7 @@
     (let ((id (car spec)))
       (or (find-library-by
             (lambda (x) (eq? id (library-id x))))
-          (error #f "cannot find library with spec ~s" spec))))
+          (error #f "cannot find library with required spec" spec))))
 
   (define label->binding-table (make-eq-hashtable))
 
@@ -205,9 +207,9 @@
           (vis-lib* (map find-library-by-spec/die vis*))
           (inv-lib* (map find-library-by-spec/die inv*)))
       (unless (and (symbol? id) (list? name) (list? ver))
-        (error 'install-library "invalid spec ~s ~s ~s" id name ver))
+        (error 'install-library "invalid spec with id/name/ver" id name ver))
       (when (library-exists? name)
-        (error 'install-library "~s is already installed" name))
+        (error 'install-library "library is already installed" name))
       (let ((lib (make-library id name ver imp-lib* vis-lib* inv-lib* 
                     exp-subst exp-env visit-code invoke-code 
                     visible?)))
@@ -231,10 +233,10 @@
     (let ((invoke (library-invoke-state lib)))
       (when (procedure? invoke)
         (set-library-invoke-state! lib 
-          (lambda () (error 'invoke "circularity detected for ~s" lib)))
+          (lambda () (error 'invoke "circularity detected" lib)))
         (for-each invoke-library (library-inv* lib))
         (set-library-invoke-state! lib 
-          (lambda () (error 'invoke "first invoke did not return for ~s" lib)))
+          (lambda () (error 'invoke "first invoke did not return" lib)))
         (invoke)
         (set-library-invoke-state! lib #t))))
 
@@ -243,10 +245,10 @@
     (let ((visit (library-visit-state lib)))
       (when (procedure? visit)
         (set-library-visit-state! lib 
-          (lambda () (error 'visit "circularity detected for ~s" lib)))
+          (lambda () (error 'visit "circularity detected" lib)))
         (for-each invoke-library (library-vis* lib))
         (set-library-visit-state! lib 
-          (lambda () (error 'invoke "first visit did not return for ~s" lib)))
+          (lambda () (error 'invoke "first visit did not return" lib)))
         (visit)
         (set-library-visit-state! lib #t))))
 
@@ -268,7 +270,7 @@
   (define library-spec       
     (lambda (x) 
       (unless (library? x)
-        (error 'library-spec "~s is not a library" x))
+        (error 'library-spec "not a library" x))
       (list (library-id x) (library-name x) (library-ver x)))) 
   )
 
diff --git a/scheme/run-tests.ss b/scheme/run-tests.ss
index 8b6603c..31b07d9 100755
--- a/scheme/run-tests.ss
+++ b/scheme/run-tests.ss
@@ -18,7 +18,7 @@
       (let-values ([(s r) (exact-integer-sqrt i)])
         (unless (and (= (+ (* s s) r) i)
                      (< i (* (+ s 1) (+ s 1))))
-          (error 'exact-integer-sqrt "wrong result for ~s" i))
+          (error 'exact-integer-sqrt "wrong result" i))
         (f (+ i inc) j inc))))
   (f 0 10000 1)
   (f 0 536870911 10000)
diff --git a/scheme/todo-r6rs.ss b/scheme/todo-r6rs.ss
index 21e02cf..5ea71bf 100755
--- a/scheme/todo-r6rs.ss
+++ b/scheme/todo-r6rs.ss
@@ -781,7 +781,7 @@
 (define (no-dups ls)
   (unless (null? ls)
     (when (memq (car ls) (cdr ls))
-      (error #f "duplicate ~s" (car ls)))
+      (error #f "duplicate identifier" (car ls)))
     (no-dups (cdr ls))))
 
 (define (assert-id x)
@@ -794,7 +794,7 @@
                       (andmap (lambda (x) 
                                 (assq x library-names))
                         libs))))
-    (error #f "invalid id ~s" x)))
+    (error #f "invalid identifier" x)))
 
 
 (define (filter* ls) 
@@ -823,7 +823,7 @@
      (lambda (x) 
        (let ([st (cadr x)] [libs (cddr x)])
          (format "(~a ~a)" st (join "," libs))))]
-    [else (error)]))
+    [else (error #f "invalid identifier" x)]))
 
 (define (print-ids ls) 
   (define (split ls n) 
@@ -914,7 +914,7 @@
                        (cond
                          [(assq x status-names)  #t]
                          [(assq x library-names) #f]
-                         [else (error #f "invalid argument ~a" x)]))
+                         [else (error #f "invalid argument" x)]))
                      (map string->symbol args))])
        (let ([ls (filter
                    (lambda (x)