diff --git a/CMakeLists.txt b/CMakeLists.txt
index b2929567..c38e5802 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -16,7 +16,7 @@ execute_process(
 
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY bin)
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY lib)
-set(CMAKE_C_FLAGS "-Wall -Wextra")
+set(CMAKE_C_FLAGS "-O2 -Wall -Wextra")
 set(CMAKE_C_FLAGS_DEBUG "-g -DDEBUG=1")
 
 option(USE_C11_FEATURE "Enable c11 feature" OFF)
diff --git a/contrib/10.regexp/src/regexp.c b/contrib/10.regexp/src/regexp.c
index 5ee5d477..1f4dcec9 100644
--- a/contrib/10.regexp/src/regexp.c
+++ b/contrib/10.regexp/src/regexp.c
@@ -182,7 +182,7 @@ pic_regexp_regexp_replace(pic_state *pic)
 void
 pic_init_regexp(pic_state *pic)
 {
-  pic_deflibrary ("(picrin regexp)") {
+  pic_deflibrary (pic, "(picrin regexp)") {
     pic_defun(pic, "regexp", pic_regexp_regexp);
     pic_defun(pic, "regexp?", pic_regexp_regexp_p);
     pic_defun(pic, "regexp-match", pic_regexp_regexp_match);
diff --git a/docs/lang.rst b/docs/lang.rst
index 3c3f463b..de380951 100644
--- a/docs/lang.rst
+++ b/docs/lang.rst
@@ -19,6 +19,7 @@ At the REPL start-up time, some usuful built-in libraries listed below will be a
 - ``(scheme time)``
 - ``(scheme case-lambda)``
 - ``(scheme read)``
+- ``(scheme eval)``
 
 Compliance with R7RS
 ---------------------
@@ -45,22 +46,22 @@ section                                          status     comments
 4.2.2 Binding constructs                         yes
 4.2.3 Sequencing                                 yes
 4.2.4 Iteration                                  yes
-4.2.5 Delayed evaluation                         N/A
+4.2.5 Delayed evaluation                         yes
 4.2.6 Dynamic bindings                           yes
-4.2.7 Exception handling                         no         ``guard`` syntax.
+4.2.7 Exception handling                         yes        ``guard`` syntax.
 4.2.8 Quasiquotation                             yes        can be safely nested. TODO: multiple argument for unquote
-4.2.9 Case-lambda                                N/A
-4.3.1 Bindings constructs for syntactic keywords incomplete [#]_
+4.2.9 Case-lambda                                yes
+4.3.1 Bindings constructs for syntactic keywords yes [#]_
 4.3.2 Pattern language                           yes        ``syntax-rules``
 4.3.3 Signaling errors in macro transformers     yes
 5.1 Programs                                     yes
-5.2 Import declarations                          incomplete only simple import declarations, no support for import with renaming.
+5.2 Import declarations                          yes
 5.3.1 Top level definitions                      yes
 5.3.2 Internal definitions                       yes        TODO: interreferential definitions
 5.3.3 Multiple-value definitions                 yes
 5.4 Syntax definitions                           yes
 5.5 Recored-type definitions                     yes
-5.6.1 Library Syntax                             incomplete In picrin, libraries can be reopend and can be nested.
+5.6.1 Library Syntax                             yes        In picrin, libraries can be reopend and can be nested.
 5.6.2 Library example                            N/A
 5.7 The REPL                                     yes
 6.1 Equivalence predicates                       yes
@@ -70,7 +71,7 @@ section                                          status     comments
 6.2.4 Implementation extensions                  yes
 6.2.5 Syntax of numerical constants              yes
 6.2.6 Numerical operations                       yes        ``denominator``, ``numerator``, and ``rationalize`` are not supported for now. Also, picrin does not provide complex library procedures.
-6.2.7 Numerical input and output                 incomplete only partial support supplied.
+6.2.7 Numerical input and output                 yes
 6.3 Booleans                                     yes
 6.4 Pairs and lists                              yes        ``list?`` is safe for using against circular list.
 6.5 Symbols                                      yes
@@ -79,12 +80,12 @@ section                                          status     comments
 6.8 Vectors                                      yes
 6.9 Bytevectors                                  yes
 6.10  Control features                           yes
-6.11 Exceptions                                  yes        ``raise-continuable`` is not supported
-6.12 Environments and evaluation                 N/A
+6.11 Exceptions                                  yes
+6.12 Environments and evaluation                 yes
 6.13.1 Ports                                     yes
 6.13.2 Input                                     yes
 6.13.3 Output                                    yes
 6.14 System interface                            yes
 ================================================ ========== ==========================================================================================================================
 
-.. [#] Picrin provides hygienic macros in addition to so-called legacy macro (``define-macro``), such as syntactic closure, explicit renaming macro, and implicit renaming macro. As of now let-syntax and letrec-syntax are not provided.
+.. [#] Picrin provides hygienic macros in addition to so-called legacy macro (``define-macro``), such as syntactic closure, explicit renaming macro, and implicit renaming macro.
diff --git a/docs/libs.rst b/docs/libs.rst
index b87d7980..f8d417c2 100644
--- a/docs/libs.rst
+++ b/docs/libs.rst
@@ -49,6 +49,7 @@ Utility functions and syntaces for macro definition.
 
 - define-macro
 - gensym
+- ungensym
 - macroexpand
 - macroexpand-1
 
@@ -68,6 +69,7 @@ Syntactic closures.
 
 - er-macro-transformer
 - ir-macro-transformer
+- strip-syntax
 
 Explicit renaming macro family.
 
diff --git a/extlib/xfile b/extlib/xfile
index 45cad164..e9d634ff 160000
--- a/extlib/xfile
+++ b/extlib/xfile
@@ -1 +1 @@
-Subproject commit 45cad164afcd0ad3f83286f39ae947c0e595c077
+Subproject commit e9d634ff99d1a954af3fa80dc2f2ccb1227b4a2b
diff --git a/extlib/xhash b/extlib/xhash
index ddc2ea28..0b5f935a 160000
--- a/extlib/xhash
+++ b/extlib/xhash
@@ -1 +1 @@
-Subproject commit ddc2ea288b37b3f5de37024ff2648d11aa18811a
+Subproject commit 0b5f935aa7a236f1ef1787f81dce7f5ba679e95b
diff --git a/include/picrin.h b/include/picrin.h
index fd3b4ca2..a1c32c1f 100644
--- a/include/picrin.h
+++ b/include/picrin.h
@@ -57,18 +57,11 @@ typedef struct {
   struct pic_env *up;
 } pic_callinfo;
 
-typedef struct pic_block {
-  struct pic_block *prev;
-  int depth;
-  struct pic_proc *in, *out;
-  unsigned refcnt;
-} pic_block;
-
 typedef struct {
   int argc;
   char **argv, **envp;
 
-  pic_block *blk;
+  struct pic_block *blk;
 
   pic_value *sp;
   pic_value *stbase, *stend;
@@ -78,6 +71,8 @@ typedef struct {
 
   pic_code *ip;
 
+  struct pic_lib *lib;
+
   pic_sym sDEFINE, sLAMBDA, sIF, sBEGIN, sQUOTE, sSETBANG;
   pic_sym sQUASIQUOTE, sUNQUOTE, sUNQUOTE_SPLICING;
   pic_sym sDEFINE_SYNTAX;
@@ -95,20 +90,17 @@ typedef struct {
   int sym_cnt;
   int uniq_sym_cnt;
 
-  xhash global_tbl;
-  pic_value *globals;
-  size_t glen, gcapa;
-
+  xhash globals;
   xhash macros;
+  pic_value libs;
 
-  pic_value lib_tbl;
-  struct pic_lib *lib;
-
+  bool rfcase;
   xhash rlabels;
 
   jmp_buf *jmp;
   struct pic_error *err;
   struct pic_jmpbuf *try_jmps;
+  size_t try_jmp_size, try_jmp_idx;
 
   struct pic_heap *heap;
   struct pic_object **arena;
@@ -151,7 +143,6 @@ pic_value pic_funcall(pic_state *pic, const char *name, pic_list args);
 struct pic_proc *pic_get_proc(pic_state *);
 int pic_get_args(pic_state *, const char *, ...);
 void pic_defun(pic_state *, const char *, pic_func_t);
-void pic_defmacro(pic_state *, const char *, struct pic_proc *);
 
 bool pic_equal_p(pic_state *, pic_value, pic_value);
 
@@ -159,6 +150,7 @@ pic_sym pic_intern(pic_state *, const char *, size_t);
 pic_sym pic_intern_cstr(pic_state *, const char *);
 const char *pic_symbol_name(pic_state *, pic_sym);
 pic_sym pic_gensym(pic_state *, pic_sym);
+pic_sym pic_ungensym(pic_state *, pic_sym);
 bool pic_interned_p(pic_state *, pic_sym);
 
 char *pic_strdup(pic_state *, const char *);
@@ -180,17 +172,17 @@ pic_value pic_apply3(pic_state *, struct pic_proc *, pic_value, pic_value, pic_v
 pic_value pic_apply4(pic_state *, struct pic_proc *, pic_value, pic_value, pic_value, pic_value);
 pic_value pic_apply5(pic_state *, struct pic_proc *, pic_value, pic_value, pic_value, pic_value, pic_value);
 pic_value pic_apply_trampoline(pic_state *, struct pic_proc *, pic_value);
-pic_value pic_eval(pic_state *, pic_value);
-struct pic_proc *pic_compile(pic_state *, pic_value);
-pic_value pic_macroexpand(pic_state *, pic_value);
+pic_value pic_eval(pic_state *, pic_value, struct pic_lib *);
+struct pic_proc *pic_compile(pic_state *, pic_value, struct pic_lib *);
+pic_value pic_macroexpand(pic_state *, pic_value, struct pic_lib *);
 
 void pic_in_library(pic_state *, pic_value);
 struct pic_lib *pic_make_library(pic_state *, pic_value);
 struct pic_lib *pic_find_library(pic_state *, pic_value);
 
-#define pic_deflibrary(spec)                                            \
-  pic_deflibrary_helper__(GENSYM(i), GENSYM(prev_lib), spec)
-#define pic_deflibrary_helper__(i, prev_lib, spec)                      \
+#define pic_deflibrary(pic, spec)                                       \
+  pic_deflibrary_helper__(pic, GENSYM(i), GENSYM(prev_lib), spec)
+#define pic_deflibrary_helper__(pic, i, prev_lib, spec)                 \
   for (int i = 0; ! i; )                                                \
     for (struct pic_lib *prev_lib; ! i; )                               \
       for ((prev_lib = pic->lib), pic_make_library(pic, pic_read_cstr(pic, spec)), pic_in_library(pic, pic_read_cstr(pic, spec)); ! i++; pic->lib = prev_lib)
diff --git a/include/picrin/config.h b/include/picrin/config.h
index 2acfe0ea..79b8fc3c 100644
--- a/include/picrin/config.h
+++ b/include/picrin/config.h
@@ -26,8 +26,6 @@
 
 /* #define PIC_RESCUE_SIZE 30 */
 
-/* #define PIC_GLOBALS_SIZE 1024 */
-
 /* #define PIC_SYM_POOL_SIZE 128 */
 
 /* #define PIC_IREP_SIZE 8 */
@@ -93,10 +91,6 @@
 # define PIC_RESCUE_SIZE 30
 #endif
 
-#ifndef PIC_GLOBALS_SIZE
-# define PIC_GLOBALS_SIZE 1024
-#endif
-
 #ifndef PIC_SYM_POOL_SIZE
 # define PIC_SYM_POOL_SIZE 128
 #endif
diff --git a/include/picrin/cont.h b/include/picrin/cont.h
index 496454fd..0a0da9f1 100644
--- a/include/picrin/cont.h
+++ b/include/picrin/cont.h
@@ -9,11 +9,18 @@
 extern "C" {
 #endif
 
+struct pic_block {
+  PIC_OBJECT_HEADER
+  struct pic_block *prev;
+  int depth;
+  struct pic_proc *in, *out;
+};
+
 struct pic_cont {
   PIC_OBJECT_HEADER
   jmp_buf jmp;
 
-  pic_block *blk;
+  struct pic_block *blk;
 
   char *stk_pos, *stk_ptr;
   ptrdiff_t stk_len;
@@ -30,37 +37,12 @@ struct pic_cont {
   size_t arena_size;
   int arena_idx;
 
+  struct pic_jmpbuf *try_jmps;
+  size_t try_jmp_idx, try_jmp_size;
+
   pic_value results;
 };
 
-#define PIC_BLK_INCREF(pic,blk) do {		\
-    (blk)->refcnt++;				\
-  } while (0)
-
-#define PIC_BLK_DECREF(pic,blk) do {			\
-    pic_block *_a = (blk), *_b;                         \
-    while (_a) {					\
-      if (! --_a->refcnt) {				\
-	_b = _a->prev;					\
-	pic_free((pic), _a);				\
-	_a = _b;					\
-      } else {						\
-	break;						\
-      }							\
-    }							\
-  } while (0)
-
-#define PIC_BLK_EXIT(pic) do {                           \
-    pic_block *_a;                                       \
-    while (pic->blk) {                                   \
-      if (pic->blk->out)                                 \
-        pic_apply0(pic, pic->blk->out);                  \
-      _a = pic->blk->prev;                               \
-      PIC_BLK_DECREF(pic, pic->blk);                     \
-      pic->blk = _a;                                     \
-    }                                                    \
-  } while (0)
-
 pic_value pic_values0(pic_state *);
 pic_value pic_values1(pic_state *, pic_value);
 pic_value pic_values2(pic_state *, pic_value, pic_value);
diff --git a/include/picrin/error.h b/include/picrin/error.h
index 75361c1a..bea590e2 100644
--- a/include/picrin/error.h
+++ b/include/picrin/error.h
@@ -11,17 +11,19 @@ extern "C" {
 
 struct pic_jmpbuf {
   jmp_buf here;
-  pic_callinfo *ci;
-  pic_value *sp;
+  struct pic_proc *handler;
+  ptrdiff_t ci_offset;
+  ptrdiff_t sp_offset;
   pic_code *ip;
   jmp_buf *prev_jmp;
-  struct pic_jmpbuf *prev;
 };
 
 /* do not return from try block! */
 
 #define pic_try                                 \
-  pic_push_try(pic);                            \
+  pic_try_with_handler(NULL)
+#define pic_try_with_handler(handler)           \
+  pic_push_try(pic, handler);                   \
   if (setjmp(*pic->jmp) == 0)                   \
     do
 #define pic_catch                               \
@@ -29,7 +31,7 @@ struct pic_jmpbuf {
   else                                          \
     if (pic_pop_try(pic), 1)
 
-void pic_push_try(pic_state *);
+void pic_push_try(pic_state *, struct pic_proc *);
 void pic_pop_try(pic_state *);
 
 noreturn void pic_throw(pic_state *, short, const char *, pic_value);
diff --git a/include/picrin/value.h b/include/picrin/value.h
index bfc9d1ca..6137c2eb 100644
--- a/include/picrin/value.h
+++ b/include/picrin/value.h
@@ -13,7 +13,7 @@ extern "C" {
  * pic_sym is just an alias to unsigned int.
  */
 
-typedef unsigned pic_sym;
+typedef int pic_sym;
 
 /**
  * `undef` values never seen from user-end: that is,
@@ -116,7 +116,8 @@ enum pic_tt {
   PIC_TT_IREP,
   PIC_TT_DATA,
   PIC_TT_DICT,
-  PIC_TT_RECORD
+  PIC_TT_RECORD,
+  PIC_TT_BLK,
 };
 
 #define PIC_OBJECT_HEADER			\
@@ -271,6 +272,8 @@ pic_type_repr(enum pic_tt tt)
     return "dict";
   case PIC_TT_RECORD:
     return "record";
+  case PIC_TT_BLK:
+    return "block";
   }
   UNREACHABLE();
 }
diff --git a/piclib/CMakeLists.txt b/piclib/CMakeLists.txt
index 9d81aae3..d7f3ab7c 100644
--- a/piclib/CMakeLists.txt
+++ b/piclib/CMakeLists.txt
@@ -8,6 +8,9 @@ list(APPEND PICLIB_SCHEME_LIBS
   ${PROJECT_SOURCE_DIR}/piclib/scheme/file.scm
   ${PROJECT_SOURCE_DIR}/piclib/scheme/case-lambda.scm
   ${PROJECT_SOURCE_DIR}/piclib/scheme/lazy.scm
+  ${PROJECT_SOURCE_DIR}/piclib/scheme/eval.scm
+  ${PROJECT_SOURCE_DIR}/piclib/scheme/r5rs.scm
+  ${PROJECT_SOURCE_DIR}/piclib/scheme/null.scm
   ${PROJECT_SOURCE_DIR}/piclib/srfi/1.scm
   ${PROJECT_SOURCE_DIR}/piclib/srfi/8.scm
   ${PROJECT_SOURCE_DIR}/piclib/srfi/26.scm
@@ -15,4 +18,7 @@ list(APPEND PICLIB_SCHEME_LIBS
   ${PROJECT_SOURCE_DIR}/piclib/srfi/60.scm
   ${PROJECT_SOURCE_DIR}/piclib/srfi/95.scm
   ${PROJECT_SOURCE_DIR}/piclib/srfi/111.scm
+
+  ${PROJECT_SOURCE_DIR}/piclib/picrin/user.scm
+  ${PROJECT_SOURCE_DIR}/piclib/picrin/repl.scm
   )
diff --git a/piclib/picrin/macro.scm b/piclib/picrin/macro.scm
index 5682d8ca..d798df0f 100644
--- a/piclib/picrin/macro.scm
+++ b/piclib/picrin/macro.scm
@@ -20,7 +20,7 @@
                     expr)))))
 
   (define (memoize f)
-    "memoize on a symbol"
+    "memoize on symbols"
     (define cache (make-dictionary))
     (lambda (sym)
       (if (dictionary-has? cache sym)
@@ -30,6 +30,10 @@
             (dictionary-set! cache sym val)
             val))))
 
+  (define (identifier=? env1 sym1 env2 sym2)
+    (eq? (make-identifier sym1 env1)
+         (make-identifier sym2 env2)))
+
   (define (make-syntactic-closure env free form)
 
     (define resolve
@@ -106,6 +110,9 @@
                   (rename sym)))
             (f (walk inject expr) inject compare))))
 
+  (define (strip-syntax form)
+    (walk ungensym form))
+
   (define-syntax define-macro
     (er-macro-transformer
      (lambda (expr r c)
@@ -120,11 +127,13 @@
                        (cons (cdr formal)
                              body)))))))
 
-  (export make-syntactic-closure
+  (export identifier=?
+          make-syntactic-closure
           close-syntax
           capture-syntactic-environment
           sc-macro-transformer
           rsc-macro-transformer
           er-macro-transformer
           ir-macro-transformer
+          strip-syntax
           define-macro))
diff --git a/piclib/picrin/repl.scm b/piclib/picrin/repl.scm
new file mode 100644
index 00000000..759421d0
--- /dev/null
+++ b/piclib/picrin/repl.scm
@@ -0,0 +1,86 @@
+(define-library (picrin repl)
+  (import (scheme base)
+          (scheme read)
+          (scheme file)
+          (scheme write)
+          (scheme eval)
+          (scheme process-context))
+
+  (define (join sep strs)
+    (let loop ((result (car strs)) (rest (cdr strs)))
+      (if (null? rest)
+          result
+          (loop (string-append result sep (car rest)) (cdr rest)))))
+
+  (define (file->string file)
+    (with-input-from-file file
+      (lambda ()
+        (let loop ((line (read-line)) (acc '()))
+          (if (eof-object? line)
+              (join "\n" (reverse acc))
+              (loop (read-line) (cons line acc)))))))
+
+  (define (print obj . port)
+    (let ((port (if (null? port) (current-output-port) (car port))))
+      (write obj port)
+      (newline port)
+      obj))
+
+  (define (print-help)
+    (display "picrin scheme\n")
+    (display "\n")
+    (display "Usage: picrin [options] [file]\n")
+    (display "\n")
+    (display "Options:\n")
+    (display "  -e [program]		run one liner script\n")
+    (display "  -h or --help		show this help\n"))
+
+  (define (getopt)
+    (let ((args (cdr (command-line))))
+      (if (null? args)
+          #f
+          (case (string->symbol (car args))
+            ((-h --help)
+             (print-help)
+             (exit 1))
+            ((-e)
+             (cadr args))
+            (else
+             (file->string (car args)))))))
+
+  (define (main-loop in out on-err)
+    (display "> " out)
+    (let ((expr (read in)))
+      (if (eof-object? expr)
+          (newline out)                 ; exit
+          (begin
+            (call/cc
+             (lambda (leave)
+              (with-exception-handler
+               (lambda (condition)
+                 (display (error-object-message condition) (current-error-port))
+                 (newline)
+                 (if on-err
+                     (on-err)
+                     (leave)))
+               (lambda ()
+                 (print (eval expr '(picrin user)) out)))))
+            (main-loop in out on-err)))))
+
+  (define (run-repl program)
+    (let ((in (if program
+                  (open-input-string program)
+                  (current-input-port)))
+          (out (if program
+                   (open-output-string) ; ignore output
+                   (current-output-port)))
+          (on-err (if program
+                      (lambda () (exit 1))
+                      #f)))
+      (main-loop in out on-err)))
+
+  (define (repl)
+    (let ((program (getopt)))
+      (run-repl program)))
+
+  (export repl))
diff --git a/piclib/picrin/test.scm b/piclib/picrin/test.scm
index 1e938e11..28650b84 100644
--- a/piclib/picrin/test.scm
+++ b/piclib/picrin/test.scm
@@ -24,7 +24,7 @@
     (for-each
      (lambda (fail)
        (display fail))
-     fails))
+     (reverse fails)))
 
   (define (test-begin . o)
     (set! test-counter (+ test-counter 1)))
@@ -83,19 +83,4 @@
     (syntax-rules ()
       ((_) (syntax-error "invalid use of test-syntax-error"))))
 
-  (define-syntax test-numeric-syntax
-    (syntax-rules ()
-      ((test-numeric-syntax str expect strs ...)
-       (let* ((z (read (open-input-string str)))
-              (out (open-output-string))
-              (z-str (begin (write z out) (get-output-string out))))
-         (test expect (values z))
-         (test #t (and (member z-str '(str strs ...)) #t))))))
-
-  ;; (define (test-read-error str)
-  ;;   (test-assert
-  ;;       (guard (exn (else #t))
-  ;;         (read (open-input-string str))
-  ;;         #f)))
-  (export test test-begin test-end test-values test-exit test-syntax-error test-numeric-syntax)
-  )
+  (export test test-begin test-end test-values test-exit test-syntax-error))
diff --git a/piclib/picrin/user.scm b/piclib/picrin/user.scm
new file mode 100644
index 00000000..db615a43
--- /dev/null
+++ b/piclib/picrin/user.scm
@@ -0,0 +1,14 @@
+;  the default repl environment
+
+(define-library (picrin user)
+  (import (scheme base)
+          (scheme load)
+          (scheme process-context)
+          (scheme read)
+          (scheme write)
+          (scheme file)
+          (scheme inexact)
+          (scheme cxr)
+          (scheme lazy)
+          (scheme time)
+          (picrin macro)))
diff --git a/piclib/prelude.scm b/piclib/prelude.scm
index b655b002..5f86d66e 100644
--- a/piclib/prelude.scm
+++ b/piclib/prelude.scm
@@ -145,19 +145,6 @@
        (let ((x (cadr form)))
          (qq 1 x)))))
 
-  #;
-  (define-syntax let*
-    (ir-macro-transformer
-     (lambda (form inject compare)
-       (let ((bindings (cadr form))
-             (body (cddr form)))
-         (if (null? bindings)
-             `(let () ,@body)
-             `(let ((,(caar bindings)
-                     ,@(cdar bindings)))
-                (let* (,@(cdr bindings))
-                  ,@body)))))))
-
   (define-syntax let*
     (er-macro-transformer
      (lambda (form r compare)
@@ -375,18 +362,6 @@
   (import (scheme base)
           (picrin macro))
 
-  (define-syntax with
-    (ir-macro-transformer
-     (lambda (form inject compare)
-       (let ((before (car (cdr form)))
-             (after  (car (cdr (cdr form))))
-             (body   (cdr (cdr (cdr form)))))
-         `(begin
-            (,before)
-            (let ((result (begin ,@body)))
-              (,after)
-              result))))))
-
   (define-syntax parameterize
     (ir-macro-transformer
      (lambda (form inject compare)
@@ -394,12 +369,11 @@
              (body   (cdr (cdr form))))
          (let ((vars (map car formal))
                (vals (map cadr formal)))
-           `(with
-             (lambda ()
-               ,@(map (lambda (var val) `(parameter-push! ,var ,val)) vars vals))
-             (lambda ()
-               ,@(map (lambda (var) `(parameter-pop! ,var)) vars))
-             ,@body))))))
+           `(begin
+              ,@(map (lambda (var val) `(parameter-push! ,var ,val)) vars vals)
+              (let ((result (begin ,@body)))
+                ,@(map (lambda (var) `(parameter-pop! ,var)) vars)
+                result)))))))
 
   (export parameterize))
 
@@ -486,11 +460,6 @@
 
 (export define-record-type)
 
-(define (fold f s xs)
-  (if (null? xs)
-      s
-      (fold f (f (car xs) s) (cdr xs))))
-
 ;;; 6.6 Characters
 
 (define-macro (define-char-transitive-predicate name op)
@@ -551,24 +520,24 @@
 
 ;;; 6.9 bytevector
 
-(define (bytevector . objs)
-  (let ((len (length objs)))
+(define (bytevector->list v start end)
+  (do ((i start (+ i 1))
+       (res '()))
+      ((= i end)
+       (reverse res))
+    (set! res (cons (bytevector-u8-ref v i) res))))
+
+(define (list->bytevector list)
+  (let ((len (length list)))
     (let ((v (make-bytevector len)))
       (do ((i 0 (+ i 1))
-	   (l objs (cdr l)))
+	   (l list (cdr l)))
 	  ((= i len)
 	   v)
 	(bytevector-u8-set! v i (car l))))))
 
-(define (bytevector->list v start end)
-    (do ((i start (+ i 1))
-	 (res '()))
-	((= i end)
-	 (reverse res))
-      (set! res (cons (bytevector-u8-ref v i) res))))
-
-(define (list->bytevector v)
-  (apply bytevector v))
+(define (bytevector . objs)
+  (list->bytevector objs))
 
 (define (utf8->string v . opts)
   (let ((start (if (pair? opts) (car opts) 0))
@@ -942,3 +911,63 @@
 (import (picrin syntax-rules))
 (export syntax-rules)
 
+(define-syntax guard-aux
+  (syntax-rules (else =>)
+    ((guard-aux reraise (else result1 result2 ...))
+     (begin result1 result2 ...))
+    ((guard-aux reraise (test => result))
+     (let ((temp test))
+       (if temp
+           (result temp)
+           reraise)))
+    ((guard-aux reraise (test => result)
+                clause1 clause2 ...)
+     (let ((temp test))
+       (if temp
+           (result temp)
+           (guard-aux reraise clause1 clause2 ...))))
+    ((guard-aux reraise (test))
+     (or test reraise))
+    ((guard-aux reraise (test) clause1 clause2 ...)
+     (let ((temp test))
+       (if temp
+           temp
+           (guard-aux reraise clause1 clause2 ...))))
+    ((guard-aux reraise (test result1 result2 ...))
+     (if test
+         (begin result1 result2 ...)
+         reraise))
+    ((guard-aux reraise
+                (test result1 result2 ...)
+                clause1 clause2 ...)
+     (if test
+         (begin result1 result2 ...)
+         (guard-aux reraise clause1 clause2 ...)))))
+
+(define-syntax guard
+  (syntax-rules ()
+    ((guard (var clause ...) e1 e2 ...)
+     ((call/cc
+       (lambda (guard-k)
+         (with-exception-handler
+          (lambda (condition)
+            ((call/cc
+              (lambda (handler-k)
+                (guard-k
+                 (lambda ()
+                   (let ((var condition))
+                     (guard-aux
+                      (handler-k
+                       (lambda ()
+                         (raise-continuable condition)))
+                      clause ...))))))))
+          (lambda ()
+            (call-with-values
+                (lambda () e1 e2 ...)
+              (lambda args
+                (guard-k
+                 (lambda ()
+                   (apply values args)))))))))))))
+
+(export guard)
+
diff --git a/piclib/scheme/eval.scm b/piclib/scheme/eval.scm
new file mode 100644
index 00000000..2a4f3b0f
--- /dev/null
+++ b/piclib/scheme/eval.scm
@@ -0,0 +1,29 @@
+(define-library (scheme eval)
+  (import (scheme base))
+
+  (define (null-environment n)
+    (if (not (= n 5))
+        (error "unsupported environment version" n)
+        '(scheme null)))
+
+  (define (scheme-report-environment n)
+    (if (not (= n 5))
+        (error "unsupported environment version" n)
+        '(scheme r5rs)))
+
+  (define environment
+    (let ((counter 0))
+      (lambda specs
+        (let ((library-name `(picrin @@my-environment ,counter)))
+          (set! counter (+ counter 1))
+          (eval
+           `(define-library ,library-name
+              ,@(map (lambda (spec)
+                       `(import ,spec))
+                     specs))
+           '(scheme base))
+          library-name))))
+
+  (export null-environment
+          scheme-report-environment
+          environment))
diff --git a/piclib/scheme/file.scm b/piclib/scheme/file.scm
index 75c8bdd9..b449e49d 100644
--- a/piclib/scheme/file.scm
+++ b/piclib/scheme/file.scm
@@ -7,5 +7,19 @@
   (define (call-with-output-file filename callback)
     (call-with-port (open-output-file filename) callback))
 
+  (define (with-input-from-file filename thunk)
+    (call-with-input-file filename
+      (lambda (port)
+        (parameterize ((current-input-port port))
+          (thunk)))))
+
+  (define (with-output-to-file filename thunk)
+    (call-with-output-file filename
+      (lambda (port)
+        (parameterize ((current-output-port port))
+          (thunk)))))
+
   (export call-with-input-file
-          call-with-output-file))
+          call-with-output-file
+          with-input-from-file
+          with-output-to-file))
diff --git a/piclib/scheme/null.scm b/piclib/scheme/null.scm
new file mode 100644
index 00000000..a949473e
--- /dev/null
+++ b/piclib/scheme/null.scm
@@ -0,0 +1,12 @@
+(define-library (scheme null)
+  (import (scheme base))
+  (export define
+          lambda
+          if
+          quote
+          quasiquote
+          unquote
+          unquote-splicing
+          begin
+          set!
+          define-syntax))
diff --git a/piclib/scheme/r5rs.scm b/piclib/scheme/r5rs.scm
new file mode 100644
index 00000000..e26a999d
--- /dev/null
+++ b/piclib/scheme/r5rs.scm
@@ -0,0 +1,118 @@
+(define-library (scheme r5rs)
+  (import (scheme base)
+          (scheme inexact)
+          (scheme write)
+          (scheme read)
+          (scheme file)
+          (scheme cxr)
+          (scheme lazy)
+          (scheme eval)
+          (scheme load))
+
+  (export * + - / < <= = > >=
+          abs acos and
+          ;; angle
+          append apply asin assoc assq assv atan
+          begin boolean?
+          caaaar caaadr caaar caadar caaddr caadr caar cadaar cadadr cadar caddar cadddr caddr cadr
+          call-with-current-continuation
+          call-with-input-file
+          call-with-output-file
+          call-with-values
+          car case cdaaar cdaadr cdaar cdadar cdaddr cdadr cdar cddaar cddadr cddar cdddar cddddr cdddr cddr cdr
+          ceiling
+          ;; char->integer char-alphabetic? char-ci<=? char-ci<? char-ci=? char-ci>=? char-ci>? char-downcase char-lower-case? char-numeric? char-ready? char-upcase char-upper-case? char-whitespace? char<=? char<? char=? char>=? char>? char?
+          close-input-port close-output-port complex? cond cons cos current-input-port current-output-port
+          define define-syntax delay
+          ;; denominator
+          display do dynamic-wind
+          eof-object? eq? equal? eqv? eval even?
+          (rename inexact exact->inexact)
+          exact? exp expt
+          floor for-each force
+          gcd
+          if
+          ;; imag-part
+          (rename exact inexact->exact)
+          inexact? input-port? integer->char integer?
+          ;; interaction-environment
+          lambda lcm length let
+          peek-char procedure?
+          quote
+          rational? read
+          ;; real-part
+          remainder round
+          scheme-report-environment
+          set! set-cdr! sqrt string->list string->symbol
+          ;; string-ci<=? string-ci=? string-ci>?
+          string-fill! string-ref string<=? string=? string>? substring symbol?
+          truncate
+          vector vector-fill! vector-ref vector? with-output-to-file write-char
+          output-port?
+          let-syntax
+          letrec-syntax
+          list->string
+          list-ref
+          list?
+          log
+          ;; make-polar
+          make-string
+          map
+          member
+          memv
+          modulo
+          newline
+          null-environment
+          number->string
+          ;; numerator
+          open-input-file
+          or
+          pair?
+          positive?
+          quasiquote
+          quotient
+          ;; rationalize
+          read-char
+          real?
+          reverse
+          let*
+          letrec
+          list
+          list->vector
+          list-tail
+          load
+          ;; magnitude
+          ;; make-rectangular
+          make-vector
+          max
+          memq
+          min
+          negative?
+          not
+          null?
+          number?
+          odd?
+          open-output-file
+          set-car!
+          sin
+          string
+          string->number
+          string-append
+          ;; string-ci<?
+          ;; string-ci>=?
+          string-copy
+          string-length
+          string-set!
+          string<?
+          string>=?
+          string?
+          symbol->string
+          tan
+          values
+          vector->list
+          vector-length
+          vector-set!
+          with-input-from-file
+          write
+          zero?
+          ))
diff --git a/src/bool.c b/src/bool.c
index 74018c63..8f8c75f1 100644
--- a/src/bool.c
+++ b/src/bool.c
@@ -42,10 +42,10 @@ internal_equal_p(pic_state *pic, pic_value x, pic_value y, size_t depth, xhash *
       pic_errorf(pic, "Stack overflow in equal\n");
     }
     if (pic_pair_p(x) || pic_vec_p(x)) {
-      if (xh_get(ht, pic_obj_ptr(x)) != NULL) {
+      if (xh_get_ptr(ht, pic_obj_ptr(x)) != NULL) {
         return true;            /* `x' was seen already.  */
       } else {
-        xh_put(ht, pic_obj_ptr(x), NULL);
+        xh_put_ptr(ht, pic_obj_ptr(x), NULL);
       }
     }
   }
diff --git a/src/codegen.c b/src/codegen.c
index a42c378a..63c7a2c9 100644
--- a/src/codegen.c
+++ b/src/codegen.c
@@ -100,7 +100,7 @@ new_analyze_state(pic_state *pic)
   /* push initial scope */
   push_scope(state, pic_nil_value());
 
-  xh_begin(&it, &pic->global_tbl);
+  xh_begin(&it, &pic->globals);
   while (xh_next(&it)) {
     pic_sym sym = xh_key(it.e, pic_sym);
     xv_push(&state->scope->locals, &sym);
@@ -291,20 +291,8 @@ static pic_value
 analyze_global_var(analyze_state *state, pic_sym sym)
 {
   pic_state *pic = state->pic;
-  xh_entry *e;
-  size_t i;
 
-  if ((e = xh_get_int(&pic->global_tbl, sym))) {
-    i = xh_val(e, size_t);
-  }
-  else {
-    i = pic->glen++;
-    if (i >= pic->gcapa) {
-      pic_error(pic, "global table overflow");
-    }
-    xh_put_int(&pic->global_tbl, sym, &i);
-  }
-  return pic_list2(pic, pic_symbol_value(state->sGREF), pic_int_value(i));
+  return pic_list2(pic, pic_symbol_value(state->sGREF), pic_sym_value(sym));
 }
 
 static pic_value
@@ -832,6 +820,7 @@ analyze_node(analyze_state *state, pic_value obj, bool tailpos)
   case PIC_TT_DATA:
   case PIC_TT_DICT:
   case PIC_TT_RECORD:
+  case PIC_TT_BLK:
     pic_errorf(pic, "invalid expression given: ~s", obj);
   }
   UNREACHABLE();
@@ -1096,7 +1085,7 @@ codegen(codegen_state *state, pic_value obj)
   sym = pic_sym(pic_car(pic, obj));
   if (sym == state->sGREF) {
     cxt->code[cxt->clen].insn = OP_GREF;
-    cxt->code[cxt->clen].u.i = pic_int(pic_list_ref(pic, obj, 1));
+    cxt->code[cxt->clen].u.i = pic_sym(pic_list_ref(pic, obj, 1));
     cxt->clen++;
     return;
   } else if (sym == state->sCREF) {
@@ -1442,7 +1431,7 @@ pic_codegen(pic_state *pic, pic_value obj)
 }
 
 struct pic_proc *
-pic_compile(pic_state *pic, pic_value obj)
+pic_compile(pic_state *pic, pic_value obj, struct pic_lib *lib)
 {
   struct pic_irep *irep;
   size_t ai = pic_gc_arena_preserve(pic);
@@ -1458,7 +1447,7 @@ pic_compile(pic_state *pic, pic_value obj)
 #endif
 
   /* macroexpand */
-  obj = pic_macroexpand(pic, obj);
+  obj = pic_macroexpand(pic, obj, lib);
 #if DEBUG
   fprintf(stdout, "## macroexpand completed\n");
   pic_debug(pic, obj);
diff --git a/src/cont.c b/src/cont.c
index 11b5a3f6..30d26568 100644
--- a/src/cont.c
+++ b/src/cont.c
@@ -10,6 +10,7 @@
 #include "picrin/proc.h"
 #include "picrin/cont.h"
 #include "picrin/pair.h"
+#include "picrin/error.h"
 
 pic_value
 pic_values0(pic_state *pic)
@@ -118,7 +119,6 @@ save_cont(pic_state *pic, struct pic_cont **c)
   cont = *c = (struct pic_cont *)pic_obj_alloc(pic, sizeof(struct pic_cont), PIC_TT_CONT);
 
   cont->blk = pic->blk;
-  PIC_BLK_INCREF(pic, cont->blk);
 
   cont->stk_len = native_stack_length(pic, &pos);
   cont->stk_pos = pos;
@@ -143,6 +143,11 @@ save_cont(pic_state *pic, struct pic_cont **c)
   cont->arena = (struct pic_object **)pic_alloc(pic, sizeof(struct pic_object *) * pic->arena_size);
   memcpy(cont->arena, pic->arena, sizeof(struct pic_object *) * pic->arena_size);
 
+  cont->try_jmp_idx = pic->try_jmp_idx;
+  cont->try_jmp_size = pic->try_jmp_size;
+  cont->try_jmps = pic_alloc(pic, sizeof(struct pic_jmpbuf) * pic->try_jmp_size);
+  memcpy(cont->try_jmps, pic->try_jmps, sizeof(struct pic_jmpbuf) * pic->try_jmp_size);
+
   cont->results = pic_undef_value();
 }
 
@@ -158,8 +163,12 @@ native_stack_extend(pic_state *pic, struct pic_cont *cont)
 noreturn static void
 restore_cont(pic_state *pic, struct pic_cont *cont)
 {
+  void pic_vm_tear_off(pic_state *);
   char v;
   struct pic_cont *tmp = cont;
+  struct pic_block *blk;
+
+  pic_vm_tear_off(pic);         /* tear off */
 
   if (&v < pic->native_stack_start) {
     if (&v > cont->stk_pos) native_stack_extend(pic, cont);
@@ -168,8 +177,7 @@ restore_cont(pic_state *pic, struct pic_cont *cont)
     if (&v > cont->stk_pos + cont->stk_len) native_stack_extend(pic, cont);
   }
 
-  PIC_BLK_DECREF(pic, pic->blk);
-  PIC_BLK_INCREF(pic, cont->blk);
+  blk = pic->blk;
   pic->blk = cont->blk;
 
   pic->stbase = (pic_value *)pic_realloc(pic, pic->stbase, sizeof(pic_value) * cont->st_len);
@@ -189,13 +197,18 @@ restore_cont(pic_state *pic, struct pic_cont *cont)
   pic->arena_size = cont->arena_size;
   pic->arena_idx = cont->arena_idx;
 
+  pic->try_jmps = pic_realloc(pic, pic->try_jmps, sizeof(struct pic_jmpbuf) * cont->try_jmp_size);
+  memcpy(pic->try_jmps, cont->try_jmps, sizeof(struct pic_jmpbuf) * cont->try_jmp_size);
+  pic->try_jmp_size = cont->try_jmp_size;
+  pic->try_jmp_idx = cont->try_jmp_idx;
+
   memcpy(cont->stk_pos, cont->stk_ptr, cont->stk_len);
 
   longjmp(tmp->jmp, 1);
 }
 
 static void
-walk_to_block(pic_state *pic, pic_block *here, pic_block *there)
+walk_to_block(pic_state *pic, struct pic_block *here, struct pic_block *there)
 {
   if (here == there)
     return;
@@ -213,7 +226,7 @@ walk_to_block(pic_state *pic, pic_block *here, pic_block *there)
 static pic_value
 pic_dynamic_wind(pic_state *pic, struct pic_proc *in, struct pic_proc *thunk, struct pic_proc *out)
 {
-  pic_block *here;
+  struct pic_block *here;
   pic_value val;
 
   if (in != NULL) {
@@ -221,17 +234,14 @@ pic_dynamic_wind(pic_state *pic, struct pic_proc *in, struct pic_proc *thunk, st
   }
 
   here = pic->blk;
-  pic->blk = (pic_block *)pic_alloc(pic, sizeof(pic_block));
+  pic->blk = (struct pic_block *)pic_obj_alloc(pic, sizeof(struct pic_block), PIC_TT_BLK);
   pic->blk->prev = here;
   pic->blk->depth = here->depth + 1;
   pic->blk->in = in;
   pic->blk->out = out;
-  pic->blk->refcnt = 1;
-  PIC_BLK_INCREF(pic, here);
 
   val = pic_apply0(pic, thunk);
 
-  PIC_BLK_DECREF(pic, pic->blk);
   pic->blk = here;
 
   if (out != NULL) {
diff --git a/src/dict.c b/src/dict.c
index 1ba9d565..1018834e 100644
--- a/src/dict.c
+++ b/src/dict.c
@@ -163,7 +163,7 @@ pic_dict_dict_for_each(pic_state *pic)
 void
 pic_init_dict(pic_state *pic)
 {
-  pic_deflibrary ("(picrin dictionary)") {
+  pic_deflibrary (pic, "(picrin dictionary)") {
     pic_defun(pic, "make-dictionary", pic_dict_dict);
     pic_defun(pic, "dictionary?", pic_dict_dict_p);
     pic_defun(pic, "dictionary-has?", pic_dict_dict_has_p);
diff --git a/src/error.c b/src/error.c
index 21f6d487..f4d46f5e 100644
--- a/src/error.c
+++ b/src/error.c
@@ -34,39 +34,41 @@ pic_warnf(pic_state *pic, const char *fmt, ...)
 }
 
 void
-pic_push_try(pic_state *pic)
+pic_push_try(pic_state *pic, struct pic_proc *handler)
 {
   struct pic_jmpbuf *try_jmp;
 
-  try_jmp = pic_alloc(pic, sizeof(struct pic_jmpbuf));
+  if (pic->try_jmp_idx >= pic->try_jmp_size) {
+    pic->try_jmp_size *= 2;
+    pic->try_jmps = pic_realloc(pic, pic->try_jmps, sizeof(struct pic_jmpbuf) * pic->try_jmp_size);
+  }
 
-  try_jmp->ci = pic->ci;
-  try_jmp->sp = pic->sp;
+  try_jmp = pic->try_jmps + pic->try_jmp_idx++;
+
+  try_jmp->handler = handler;
+
+  try_jmp->ci_offset = pic->ci - pic->cibase;
+  try_jmp->sp_offset = pic->sp - pic->stbase;
   try_jmp->ip = pic->ip;
 
   try_jmp->prev_jmp = pic->jmp;
   pic->jmp = &try_jmp->here;
-
-  try_jmp->prev = pic->try_jmps;
-  pic->try_jmps = try_jmp;
 }
 
 void
 pic_pop_try(pic_state *pic)
 {
-  struct pic_jmpbuf *prev;
+  struct pic_jmpbuf *try_jmp;
 
-  assert(pic->jmp == &pic->try_jmps->here);
+  try_jmp = pic->try_jmps + --pic->try_jmp_idx;
 
-  pic->ci = pic->try_jmps->ci;
-  pic->sp = pic->try_jmps->sp;
-  pic->ip = pic->try_jmps->ip;
+  /* assert(pic->jmp == &try_jmp->here); */
 
-  pic->jmp = pic->try_jmps->prev_jmp;
+  pic->ci = try_jmp->ci_offset + pic->cibase;
+  pic->sp = try_jmp->sp_offset + pic->stbase;
+  pic->ip = try_jmp->ip;
 
-  prev = pic->try_jmps->prev;
-  pic_free(pic, pic->try_jmps);
-  pic->try_jmps = prev;
+  pic->jmp = try_jmp->prev_jmp;
 }
 
 static struct pic_error *
@@ -89,11 +91,16 @@ error_new(pic_state *pic, short type, pic_str *msg, pic_value irrs)
 noreturn void
 pic_throw_error(pic_state *pic, struct pic_error *e)
 {
+  void pic_vm_tear_off(pic_state *);
+
+  pic_vm_tear_off(pic);         /* tear off */
+
   pic->err = e;
   if (! pic->jmp) {
     puts(pic_errmsg(pic));
     abort();
   }
+
   longjmp(*pic->jmp, 1);
 }
 
@@ -140,14 +147,20 @@ pic_error_with_exception_handler(pic_state *pic)
 
   pic_get_args(pic, "ll", &handler, &thunk);
 
-  pic_try {
+  pic_try_with_handler(handler) {
     v = pic_apply0(pic, thunk);
   }
   pic_catch {
     struct pic_error *e = pic->err;
 
     pic->err = NULL;
-    v = pic_apply1(pic, handler, pic_obj_value(e));
+
+    if (e->type == PIC_ERROR_RAISED) {
+      v = pic_list_ref(pic, e->irrs, 0);
+    } else {
+      v = pic_obj_value(e);
+    }
+    v = pic_apply1(pic, handler, v);
     pic_errorf(pic, "error handler returned ~s, by error ~s", v, pic_obj_value(e));
   }
   return v;
@@ -163,6 +176,27 @@ pic_error_raise(pic_state *pic)
   pic_throw(pic, PIC_ERROR_RAISED, "object is raised", pic_list1(pic, v));
 }
 
+static pic_value
+pic_error_raise_continuable(pic_state *pic)
+{
+  pic_value v;
+
+  pic_get_args(pic, "o", &v);
+
+  if (pic->try_jmp_idx == 0) {
+    pic_errorf(pic, "no exception handler registered");
+  }
+  if (pic->try_jmps[pic->try_jmp_idx - 1].handler == NULL) {
+    pic_errorf(pic, "uncontinuable exception handler is on top");
+  }
+  else {
+    pic->try_jmp_idx--;
+    v = pic_apply1(pic, pic->try_jmps[pic->try_jmp_idx].handler, v);
+    ++pic->try_jmp_idx;
+  }
+  return v;
+}
+
 noreturn static pic_value
 pic_error_error(pic_state *pic)
 {
@@ -242,6 +276,7 @@ pic_init_error(pic_state *pic)
 {
   pic_defun(pic, "with-exception-handler", pic_error_with_exception_handler);
   pic_defun(pic, "raise", pic_error_raise);
+  pic_defun(pic, "raise-continuable", pic_error_raise_continuable);
   pic_defun(pic, "error", pic_error_error);
   pic_defun(pic, "error-object?", pic_error_error_object_p);
   pic_defun(pic, "error-object-message", pic_error_error_object_message);
diff --git a/src/eval.c b/src/eval.c
new file mode 100644
index 00000000..5a037c94
--- /dev/null
+++ b/src/eval.c
@@ -0,0 +1,39 @@
+/**
+ * See Copyright Notice in picrin.h
+ */
+
+#include "picrin.h"
+#include "picrin/macro.h"
+
+pic_value
+pic_eval(pic_state *pic, pic_value program, struct pic_lib *lib)
+{
+  struct pic_proc *proc;
+
+  proc = pic_compile(pic, program, lib);
+
+  return pic_apply(pic, proc, pic_nil_value());
+}
+
+static pic_value
+pic_eval_eval(pic_state *pic)
+{
+  pic_value program, spec;
+  struct pic_lib *lib;
+
+  pic_get_args(pic, "oo", &program, &spec);
+
+  lib = pic_find_library(pic, spec);
+  if (lib == NULL) {
+    pic_errorf(pic, "no library found: ~s", spec);
+  }
+  return pic_eval(pic, program, lib);
+}
+
+void
+pic_init_eval(pic_state *pic)
+{
+  pic_deflibrary (pic, "(scheme eval)") {
+    pic_defun(pic, "eval", pic_eval_eval);
+  }
+}
diff --git a/src/file.c b/src/file.c
index 8f55a4d1..befac195 100644
--- a/src/file.c
+++ b/src/file.c
@@ -4,6 +4,13 @@
 
 #include "picrin.h"
 #include "picrin/port.h"
+#include "picrin/error.h"
+
+static noreturn void
+file_error(pic_state *pic, const char *msg)
+{
+  pic_throw(pic, PIC_ERROR_FILE, msg, pic_nil_value());
+}
 
 static pic_value
 generic_open_file(pic_state *pic, const char *fname, char *mode, short flags)
@@ -13,7 +20,7 @@ generic_open_file(pic_state *pic, const char *fname, char *mode, short flags)
 
   file = xfopen(fname, mode);
   if (! file) {
-    pic_error(pic, "could not open file");
+    file_error(pic, "could not open file");
   }
 
   port = (struct pic_port *)pic_obj_alloc(pic, sizeof(struct pic_port), PIC_TT_PORT);
@@ -93,7 +100,7 @@ pic_file_delete(pic_state *pic)
   pic_get_args(pic, "z", &fname);
 
   if (remove(fname) != 0) {
-    pic_error(pic, "file cannot be deleted");
+    file_error(pic, "file cannot be deleted");
   }
   return pic_none_value();
 }
@@ -101,7 +108,7 @@ pic_file_delete(pic_state *pic)
 void
 pic_init_file(pic_state *pic)
 {
-  pic_deflibrary ("(scheme file)") {
+  pic_deflibrary (pic, "(scheme file)") {
     pic_defun(pic, "open-input-file", pic_file_open_input_file);
     pic_defun(pic, "open-input-binary-file", pic_file_open_input_binary_file);
     pic_defun(pic, "open-output-file", pic_file_open_output_file);
diff --git a/src/gc.c b/src/gc.c
index dcebb4e2..c302fd0d 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -323,18 +323,6 @@ gc_free(pic_state *pic, union header *bp)
 static void gc_mark(pic_state *, pic_value);
 static void gc_mark_object(pic_state *pic, struct pic_object *obj);
 
-static void
-gc_mark_block(pic_state *pic, pic_block *blk)
-{
-  while (blk) {
-    if (blk->in)
-      gc_mark_object(pic, (struct pic_object *)blk->in);
-    if (blk->out)
-      gc_mark_object(pic, (struct pic_object *)blk->out);
-    blk = blk->prev;
-  }
-}
-
 static bool
 gc_is_marked(union header *p)
 {
@@ -416,10 +404,10 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
     struct pic_cont *cont = (struct pic_cont *)obj;
     pic_value *stack;
     pic_callinfo *ci;
-    int i;
+    size_t i;
 
     /* block */
-    gc_mark_block(pic, cont->blk);
+    gc_mark_object(pic, (struct pic_object *)cont->blk);
 
     /* stack */
     for (stack = cont->st_ptr; stack != cont->st_ptr + cont->sp_offset; ++stack) {
@@ -434,10 +422,17 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
     }
 
     /* arena */
-    for (i = 0; i < cont->arena_idx; ++i) {
+    for (i = 0; i < (size_t)cont->arena_idx; ++i) {
       gc_mark_object(pic, cont->arena[i]);
     }
 
+    /* error handlers */
+    for (i = 0; i < cont->try_jmp_idx; ++i) {
+      if (cont->try_jmps[i].handler) {
+        gc_mark_object(pic, (struct pic_object *)cont->try_jmps[i].handler);
+      }
+    }
+
     /* result values */
     gc_mark(pic, cont->results);
     break;
@@ -518,6 +513,20 @@ gc_mark_object(pic_state *pic, struct pic_object *obj)
     }
     break;
   }
+  case PIC_TT_BLK: {
+    struct pic_block *blk = (struct pic_block *)obj;
+
+    if (blk->prev) {
+      gc_mark_object(pic, (struct pic_object *)blk->prev);
+    }
+    if (blk->in) {
+      gc_mark_object(pic, (struct pic_object *)blk->in);
+    }
+    if (blk->out) {
+      gc_mark_object(pic, (struct pic_object *)blk->out);
+    }
+    break;
+  }
   case PIC_TT_NIL:
   case PIC_TT_BOOL:
   case PIC_TT_FLOAT:
@@ -551,7 +560,9 @@ gc_mark_phase(pic_state *pic)
   xh_iter it;
 
   /* block */
-  gc_mark_block(pic, pic->blk);
+  if (pic->blk) {
+    gc_mark_object(pic, (struct pic_object *)pic->blk);
+  }
 
   /* stack */
   for (stack = pic->stbase; stack != pic->sp; ++stack) {
@@ -576,8 +587,9 @@ gc_mark_phase(pic_state *pic)
   }
 
   /* global variables */
-  for (i = 0; i < pic->glen; ++i) {
-    gc_mark(pic, pic->globals[i]);
+  xh_begin(&it, &pic->globals);
+  while (xh_next(&it)) {
+    gc_mark(pic, xh_val(it.e, pic_value));
   }
 
   /* macro objects */
@@ -586,8 +598,15 @@ gc_mark_phase(pic_state *pic)
     gc_mark_object(pic, xh_val(it.e, struct pic_object *));
   }
 
+  /* error handlers */
+  for (i = 0; i < pic->try_jmp_idx; ++i) {
+    if (pic->try_jmps[i].handler) {
+      gc_mark_object(pic, (struct pic_object *)pic->try_jmps[i].handler);
+    }
+  }
+
   /* library table */
-  gc_mark(pic, pic->lib_tbl);
+  gc_mark(pic, pic->libs);
 }
 
 static void
@@ -633,7 +652,7 @@ gc_finalize_object(pic_state *pic, struct pic_object *obj)
     pic_free(pic, cont->st_ptr);
     pic_free(pic, cont->ci_ptr);
     pic_free(pic, cont->arena);
-    PIC_BLK_DECREF(pic, cont->blk);
+    pic_free(pic, cont->try_jmps);
     break;
   }
   case PIC_TT_SENV: {
@@ -675,6 +694,9 @@ gc_finalize_object(pic_state *pic, struct pic_object *obj)
     xh_destroy(&rec->hash);
     break;
   }
+  case PIC_TT_BLK: {
+    break;
+  }
   case PIC_TT_NIL:
   case PIC_TT_BOOL:
   case PIC_TT_FLOAT:
diff --git a/src/init.c b/src/init.c
index 8afd5a44..f9c8dba8 100644
--- a/src/init.c
+++ b/src/init.c
@@ -32,6 +32,8 @@ void pic_init_write(pic_state *);
 void pic_init_read(pic_state *);
 void pic_init_dict(pic_state *);
 void pic_init_record(pic_state *);
+void pic_init_eval(pic_state *);
+void pic_init_lib(pic_state *);
 void pic_init_contrib(pic_state *);
 
 void pic_load_piclib(pic_state *);
@@ -60,7 +62,7 @@ pic_init_core(pic_state *pic)
 {
   size_t ai = pic_gc_arena_preserve(pic);
 
-  pic_deflibrary ("(scheme base)") {
+  pic_deflibrary (pic, "(scheme base)") {
 
     /* load core syntaces */
     pic->lib->env = pic_null_syntactic_environment(pic);
@@ -94,6 +96,8 @@ pic_init_core(pic_state *pic)
     pic_init_read(pic); DONE;
     pic_init_dict(pic); DONE;
     pic_init_record(pic); DONE;
+    pic_init_eval(pic); DONE;
+    pic_init_lib(pic); DONE;
 
     pic_load_piclib(pic); DONE;
 
diff --git a/src/lib.c b/src/lib.c
index 7a197c87..b45bb71a 100644
--- a/src/lib.c
+++ b/src/lib.c
@@ -6,6 +6,9 @@
 #include "picrin/lib.h"
 #include "picrin/pair.h"
 #include "picrin/macro.h"
+#include "picrin/error.h"
+#include "picrin/dict.h"
+#include "picrin/string.h"
 
 struct pic_lib *
 pic_make_library(pic_state *pic, pic_value name)
@@ -32,7 +35,7 @@ pic_make_library(pic_state *pic, pic_value name)
   xh_init_int(&lib->exports, sizeof(pic_sym));
 
   /* register! */
-  pic->lib_tbl = pic_acons(pic, name, pic_obj_value(lib), pic->lib_tbl);
+  pic->libs = pic_acons(pic, name, pic_obj_value(lib), pic->libs);
 
   return lib;
 }
@@ -54,62 +57,204 @@ pic_find_library(pic_state *pic, pic_value spec)
 {
   pic_value v;
 
-  v = pic_assoc(pic, spec, pic->lib_tbl, NULL);
+  v = pic_assoc(pic, spec, pic->libs, NULL);
   if (pic_false_p(v)) {
     return NULL;
   }
   return pic_lib_ptr(pic_cdr(pic, v));
 }
 
-void
-pic_import(pic_state *pic, pic_value spec)
+static struct pic_dict *
+import_table(pic_state *pic, pic_value spec)
 {
+  const pic_sym sONLY = pic_intern_cstr(pic, "only");
+  const pic_sym sRENAME = pic_intern_cstr(pic, "rename");
+  const pic_sym sPREFIX = pic_intern_cstr(pic, "prefix");
+  const pic_sym sEXCEPT = pic_intern_cstr(pic, "except");
   struct pic_lib *lib;
+  struct pic_dict *imports, *dict;
+  pic_value val, id;
   xh_iter it;
 
+  imports = pic_dict_new(pic);
+
+  if (pic_list_p(spec)) {
+    if (pic_eq_p(pic_car(pic, spec), pic_sym_value(sONLY))) {
+      dict = import_table(pic, pic_cadr(pic, spec));
+      pic_for_each (val, pic_cddr(pic, spec)) {
+        pic_dict_set(pic, imports, pic_sym(val), pic_dict_ref(pic, dict, pic_sym(val)));
+      }
+      return imports;
+    }
+    if (pic_eq_p(pic_car(pic, spec), pic_sym_value(sRENAME))) {
+      imports = import_table(pic, pic_cadr(pic, spec));
+      pic_for_each (val, pic_cddr(pic, spec)) {
+        id = pic_dict_ref(pic, imports, pic_sym(pic_car(pic, val)));
+        pic_dict_del(pic, imports, pic_sym(pic_car(pic, val)));
+        pic_dict_set(pic, imports, pic_sym(pic_cadr(pic, val)), id);
+      }
+      return imports;
+    }
+    if (pic_eq_p(pic_car(pic, spec), pic_sym_value(sPREFIX))) {
+      dict = import_table(pic, pic_cadr(pic, spec));
+      xh_begin(&it, &dict->hash);
+      while (xh_next(&it)) {
+        pic_dict_set(pic, imports, pic_intern_cstr(pic, pic_str_cstr(pic_strcat(pic, pic_str_new_cstr(pic, pic_symbol_name(pic, pic_sym(pic_car(pic, pic_cddr(pic, spec))))), pic_str_new_cstr(pic, pic_symbol_name(pic, xh_key(it.e, pic_sym)))))), xh_val(it.e, pic_value));
+      }
+      return imports;
+    }
+    if (pic_eq_p(pic_car(pic, spec), pic_sym_value(sEXCEPT))) {
+      imports = import_table(pic, pic_cadr(pic, spec));
+      pic_for_each (val, pic_cddr(pic, spec)) {
+        pic_dict_del(pic, imports, pic_sym(val));
+      }
+      return imports;
+    }
+  }
   lib = pic_find_library(pic, spec);
   if (! lib) {
     pic_errorf(pic, "library not found: ~a", spec);
   }
   xh_begin(&it, &lib->exports);
   while (xh_next(&it)) {
+    pic_dict_set(pic, imports, xh_key(it.e, pic_sym), pic_sym_value(xh_val(it.e, pic_sym)));
+  }
+  return imports;
+}
+
+static void
+import(pic_state *pic, pic_value spec)
+{
+  struct pic_dict *imports;
+  xh_iter it;
+
+  imports = import_table(pic, spec);
+
+  xh_begin(&it, &imports->hash);
+  while (xh_next(&it)) {
 
 #if DEBUG
-    printf("* importing %s as %s\n", pic_symbol_name(pic, xh_key(it.e, pic_sym)), pic_symbol_name(pic, xh_val(it.e, pic_sym)));
+    printf("* importing %s as %s\n", pic_symbol_name(pic, xh_key(it.e, pic_sym)), pic_symbol_name(pic, pic_sym(xh_val(it.e, pic_value))));
 #endif
 
-    pic_put_rename(pic, pic->lib->env, xh_key(it.e, pic_sym), xh_val(it.e, pic_sym));
+    pic_put_rename(pic, pic->lib->env, xh_key(it.e, pic_sym), pic_sym(xh_val(it.e, pic_value)));
   }
 }
 
+static void
+export(pic_state *pic, pic_value spec)
+{
+  const pic_sym sRENAME = pic_intern_cstr(pic, "rename");
+  pic_value a, b;
+  pic_sym rename;
+
+  if (pic_sym_p(spec)) {        /* (export a) */
+    a = b = spec;
+  } else {                      /* (export (rename a b)) */
+    if (! pic_list_p(spec))
+      goto fail;
+    if (! pic_length(pic, spec) == 3)
+      goto fail;
+    if (! pic_eq_p(pic_car(pic, spec), pic_sym_value(sRENAME)))
+      goto fail;
+    if (! pic_sym_p(a = pic_list_ref(pic, spec, 1)))
+      goto fail;
+    if (! pic_sym_p(b = pic_list_ref(pic, spec, 2)))
+      goto fail;
+  }
+
+  if (! pic_find_rename(pic, pic->lib->env, pic_sym(a), &rename)) {
+    pic_errorf(pic, "export: symbol not defined %s", pic_symbol_name(pic, pic_sym(a)));
+  }
+
+#if DEBUG
+  printf("* exporting %s as %s\n", pic_symbol_name(pic, pic_sym(b)), pic_symbol_name(pic, rename));
+#endif
+
+  xh_put_int(&pic->lib->exports, pic_sym(b), &rename);
+
+  return;
+
+ fail:
+  pic_errorf(pic, "illegal export spec: ~s", spec);
+}
+
+void
+pic_import(pic_state *pic, pic_value spec)
+{
+  import(pic, spec);
+}
+
 void
 pic_export(pic_state *pic, pic_sym sym)
 {
-  pic_sym rename;
+  export(pic, pic_sym_value(sym));
+}
 
-  if (! pic_find_rename(pic, pic->lib->env, sym, &rename)) {
-    pic_errorf(pic, "export: symbol not defined %s", pic_symbol_name(pic, sym));
+static pic_value
+pic_lib_import(pic_state *pic)
+{
+  size_t argc, i;
+  pic_value *argv;
+
+  pic_get_args(pic, "*", &argc, &argv);
+
+  for (i = 0; i < argc; ++i) {
+    import(pic, argv[i]);
   }
 
-#if DEBUG
-  printf("* exporting %s as %s\n", pic_symbol_name(pic, sym), pic_symbol_name(pic, rename));
-#endif
+  return pic_none_value();
+}
 
-  xh_put_int(&pic->lib->exports, sym, &rename);
+static pic_value
+pic_lib_export(pic_state *pic)
+{
+  size_t argc, i;
+  pic_value *argv;
+
+  pic_get_args(pic, "*", &argc, &argv);
+
+  for (i = 0; i < argc; ++i) {
+    export(pic, argv[i]);
+  }
+
+  return pic_none_value();
+}
+
+static pic_value
+pic_lib_define_library(pic_state *pic)
+{
+  struct pic_lib *prev = pic->lib;
+  size_t argc, i;
+  pic_value spec, *argv;
+
+  pic_get_args(pic, "o*", &spec, &argc, &argv);
+
+  pic_make_library(pic, spec);
+
+  pic_try {
+    pic_in_library(pic, spec);
+
+    for (i = 0; i < argc; ++i) {
+      pic_void(pic_eval(pic, argv[i], pic->lib));
+    }
+
+    pic_in_library(pic, prev->name);
+  }
+  pic_catch {
+    pic_in_library(pic, prev->name); /* restores pic->lib even if an error occurs */
+    pic_throw_error(pic, pic->err);
+  }
+
+  return pic_none_value();
 }
 
 void
-pic_export_as(pic_state *pic, pic_sym sym, pic_sym as)
+pic_init_lib(pic_state *pic)
 {
-  pic_sym rename;
+  void pic_defmacro(pic_state *, pic_sym, pic_sym, pic_func_t);
 
-  if (! pic_find_rename(pic, pic->lib->env, sym, &rename)) {
-    pic_errorf(pic, "export: symbol not defined %s", pic_symbol_name(pic, sym));
-  }
-
-#if DEBUG
-  printf("* exporting %s as %s\n", pic_symbol_name(pic, as), pic_symbol_name(pic, rename));
-#endif
-
-  xh_put_int(&pic->lib->exports, as, &rename);
+  pic_defmacro(pic, pic->sIMPORT, pic->rIMPORT, pic_lib_import);
+  pic_defmacro(pic, pic->sEXPORT, pic->rEXPORT, pic_lib_export);
+  pic_defmacro(pic, pic->sDEFINE_LIBRARY, pic->rDEFINE_LIBRARY, pic_lib_define_library);
 }
diff --git a/src/load.c b/src/load.c
index f4b4db73..440b45e2 100644
--- a/src/load.c
+++ b/src/load.c
@@ -20,7 +20,7 @@ pic_load_cstr(pic_state *pic, const char *src)
   pic_for_each (v, exprs) {
     ai = pic_gc_arena_preserve(pic);
 
-    proc = pic_compile(pic, v);
+    proc = pic_compile(pic, v, pic->lib);
     if (proc == NULL) {
       pic_error(pic, "load: compilation failure");
     }
@@ -54,7 +54,7 @@ pic_load(pic_state *pic, const char *fn)
   pic_for_each (v, exprs) {
     ai = pic_gc_arena_preserve(pic);
 
-    proc = pic_compile(pic, v);
+    proc = pic_compile(pic, v, pic->lib);
     if (proc == NULL) {
       pic_error(pic, "load: compilation failure");
     }
@@ -81,7 +81,7 @@ pic_load_load(pic_state *pic)
 void
 pic_init_load(pic_state *pic)
 {
-  pic_deflibrary ("(scheme load)") {
+  pic_deflibrary (pic, "(scheme load)") {
     pic_defun(pic, "load", pic_load_load);
   }
 }
diff --git a/src/macro.c b/src/macro.c
index c181545a..2253533b 100644
--- a/src/macro.c
+++ b/src/macro.c
@@ -104,83 +104,6 @@ macroexpand_quote(pic_state *pic, pic_value expr)
   return pic_cons(pic, pic_sym_value(pic->rQUOTE), pic_cdr(pic, expr));
 }
 
-static pic_value
-macroexpand_import(pic_state *pic, pic_value expr)
-{
-  pic_value spec;
-
-  pic_for_each (spec, pic_cdr(pic, expr)) {
-    pic_import(pic, spec);
-  }
-
-  return pic_none_value();
-}
-
-static pic_value
-macroexpand_export(pic_state *pic, pic_value expr)
-{
-  extern pic_value pic_export_as(pic_state *, pic_sym, pic_sym);
-  pic_value spec;
-  pic_sym sRENAME, sym, as;
-
-  sRENAME = pic_intern_cstr(pic, "rename");
-
-  pic_for_each (spec, pic_cdr(pic, expr)) {
-    if (pic_sym_p(spec)) {
-      sym = as = pic_sym(spec);
-    }
-    else if (pic_list_p(spec) && pic_eq_p(pic_car(pic, spec), pic_sym_value(sRENAME))) {
-      if (pic_length(pic, spec) != 3) {
-        pic_error(pic, "syntax error");
-      }
-      if (! pic_sym_p(pic_list_ref(pic, spec, 1))) {
-        pic_error(pic, "syntax error");
-      }
-      sym = pic_sym(pic_list_ref(pic, spec, 1));
-      if (! pic_sym_p(pic_list_ref(pic, spec, 2))) {
-        pic_error(pic, "syntax error");
-      }
-      as = pic_sym(pic_list_ref(pic, spec, 2));
-    }
-    else {
-      pic_error(pic, "syntax error");
-    }
-    /* TODO: warn if symbol is shadowed by local variable */
-    pic_export_as(pic, sym, as);
-  }
-
-  return pic_none_value();
-}
-
-static pic_value
-macroexpand_deflibrary(pic_state *pic, pic_value expr)
-{
-  struct pic_lib *prev = pic->lib;
-  pic_value v;
-
-  if (pic_length(pic, expr) < 2) {
-    pic_error(pic, "syntax error");
-  }
-
-  pic_make_library(pic, pic_cadr(pic, expr));
-
-  pic_try {
-    pic_in_library(pic, pic_cadr(pic, expr));
-
-    pic_for_each (v, pic_cddr(pic, expr)) {
-      pic_void(pic_eval(pic, v));
-    }
-
-    pic_in_library(pic, prev->name);
-  }
-  pic_catch {
-    pic_in_library(pic, prev->name); /* restores pic->lib even if an error occurs */
-    pic_throw_error(pic, pic->err);
-  }
-
-  return pic_none_value();
-}
-
 static pic_value
 macroexpand_list(pic_state *pic, pic_value obj, struct pic_senv *senv)
 {
@@ -286,12 +209,14 @@ macroexpand_defsyntax(pic_state *pic, pic_value expr, struct pic_senv *senv)
   sym = pic_sym(var);
   if (! pic_find_rename(pic, senv, sym, &rename)) {
     rename = pic_add_rename(pic, senv, sym);
+  } else {
+    pic_warnf(pic, "redefining syntax variable: ~s", pic_sym_value(sym));
   }
 
   val = pic_cadr(pic, pic_cdr(pic, expr));
 
   pic_try {
-    val = pic_eval(pic, val);
+    val = pic_eval(pic, val, pic->lib);
   } pic_catch {
     pic_errorf(pic, "macroexpand error while definition: %s", pic_errmsg(pic));
   }
@@ -318,8 +243,7 @@ macroexpand_macro(pic_state *pic, struct pic_macro *mac, pic_value expr, struct
 
   if (mac->senv == NULL) { /* legacy macro */
     args = pic_cdr(pic, expr);
-  }
-  else {
+  } else {
     args = pic_list3(pic, expr, pic_obj_value(senv), pic_obj_value(mac->senv));
   }
 
@@ -335,18 +259,12 @@ macroexpand_macro(pic_state *pic, struct pic_macro *mac, pic_value expr, struct
   puts("");
 #endif
 
-  return macroexpand(pic, v, senv);
+  return v;
 }
 
 static pic_value
 macroexpand_node(pic_state *pic, pic_value expr, struct pic_senv *senv)
 {
-#if DEBUG
-  printf("[macroexpand] expanding... ");
-  pic_debug(pic, expr);
-  puts("");
-#endif
-
   switch (pic_type(expr)) {
   case PIC_TT_SYMBOL: {
     return macroexpand_symbol(pic, pic_sym(expr), senv);
@@ -363,16 +281,7 @@ macroexpand_node(pic_state *pic, pic_value expr, struct pic_senv *senv)
     if (pic_sym_p(car)) {
       pic_sym tag = pic_sym(car);
 
-      if (tag == pic->rDEFINE_LIBRARY) {
-        return macroexpand_deflibrary(pic, expr);
-      }
-      else if (tag == pic->rIMPORT) {
-        return macroexpand_import(pic, expr);
-      }
-      else if (tag == pic->rEXPORT) {
-        return macroexpand_export(pic, expr);
-      }
-      else if (tag == pic->rDEFINE_SYNTAX) {
+      if (tag == pic->rDEFINE_SYNTAX) {
         return macroexpand_defsyntax(pic, expr, senv);
       }
       else if (tag == pic->rLAMBDA) {
@@ -386,40 +295,15 @@ macroexpand_node(pic_state *pic, pic_value expr, struct pic_senv *senv)
       }
 
       if ((mac = find_macro(pic, tag)) != NULL) {
-        return macroexpand_macro(pic, mac, expr, senv);
+        return macroexpand_node(pic, macroexpand_macro(pic, mac, expr, senv), senv);
       }
     }
 
     return pic_cons(pic, car, macroexpand_list(pic, pic_cdr(pic, expr), senv));
   }
-  case PIC_TT_EOF:
-  case PIC_TT_NIL:
-  case PIC_TT_BOOL:
-  case PIC_TT_FLOAT:
-  case PIC_TT_INT:
-  case PIC_TT_CHAR:
-  case PIC_TT_STRING:
-  case PIC_TT_VECTOR:
-  case PIC_TT_BLOB: {
+  default:
     return expr;
   }
-  case PIC_TT_PROC:
-  case PIC_TT_PORT:
-  case PIC_TT_ERROR:
-  case PIC_TT_ENV:
-  case PIC_TT_CONT:
-  case PIC_TT_UNDEF:
-  case PIC_TT_SENV:
-  case PIC_TT_MACRO:
-  case PIC_TT_LIB:
-  case PIC_TT_VAR:
-  case PIC_TT_IREP:
-  case PIC_TT_DATA:
-  case PIC_TT_DICT:
-  case PIC_TT_RECORD:
-    pic_errorf(pic, "unexpected value type: ~s", expr);
-  }
-  UNREACHABLE();
 }
 
 static pic_value
@@ -428,6 +312,12 @@ macroexpand(pic_state *pic, pic_value expr, struct pic_senv *senv)
   size_t ai = pic_gc_arena_preserve(pic);
   pic_value v;
 
+#if DEBUG
+  printf("[macroexpand] expanding... ");
+  pic_debug(pic, expr);
+  puts("");
+#endif
+
   v = macroexpand_node(pic, expr, senv);
 
   pic_gc_arena_restore(pic, ai);
@@ -436,8 +326,9 @@ macroexpand(pic_state *pic, pic_value expr, struct pic_senv *senv)
 }
 
 pic_value
-pic_macroexpand(pic_state *pic, pic_value expr)
+pic_macroexpand(pic_state *pic, pic_value expr, struct pic_lib *lib)
 {
+  struct pic_lib *prev;
   pic_value v;
 
 #if DEBUG
@@ -446,7 +337,13 @@ pic_macroexpand(pic_state *pic, pic_value expr)
   puts("");
 #endif
 
-  v = macroexpand(pic, expr, pic->lib->env);
+  /* change library for macro-expansion time processing */
+  prev = pic->lib;
+  pic->lib = lib;
+
+  v = macroexpand(pic, expr, lib->env);
+
+  pic->lib = prev;
 
 #if DEBUG
   puts("after expand:");
@@ -457,47 +354,6 @@ pic_macroexpand(pic_state *pic, pic_value expr)
   return v;
 }
 
-static pic_value
-macroexpand_one(pic_state *pic, pic_value expr, struct pic_senv *senv)
-{
-  struct pic_macro *mac;
-  pic_value v, args;
-
-  if (pic_sym_p(expr)) {
-    pic_sym sym;
-
-    sym = pic_sym(expr);
-
-    if (pic_interned_p(pic, sym)) {
-      return pic_sym_value(make_identifier(pic, pic_sym(expr), senv));
-    }
-  }
-  if (pic_pair_p(expr) && pic_sym_p(pic_car(pic, expr))) {
-    pic_sym sym;
-
-    sym = make_identifier(pic, pic_sym(pic_car(pic, expr)), senv);
-
-    if ((mac = find_macro(pic, sym)) != NULL) {
-      if (mac->senv == NULL) { /* legacy macro */
-        args = pic_cdr(pic, expr);
-      }
-      else {
-        args = pic_list3(pic, expr, pic_obj_value(senv), pic_obj_value(mac->senv));
-      }
-
-      pic_try {
-        v = pic_apply(pic, mac->proc, args);
-      } pic_catch {
-        pic_errorf(pic, "macroexpand error while application: %s", pic_errmsg(pic));
-      }
-
-      return v;
-    }
-  }
-
-  return pic_undef_value();     /* no expansion occurred */
-}
-
 struct pic_senv *
 pic_senv_new(pic_state *pic, struct pic_senv *up)
 {
@@ -535,17 +391,15 @@ pic_define_syntactic_keyword(pic_state *pic, struct pic_senv *senv, pic_sym sym,
 }
 
 void
-pic_defmacro(pic_state *pic, const char *name, struct pic_proc *macro)
+pic_defmacro(pic_state *pic, pic_sym name, pic_sym id, pic_func_t func)
 {
-  pic_sym sym, rename;
+  pic_put_rename(pic, pic->lib->env, name, id);
 
   /* symbol registration */
-  sym = pic_intern_cstr(pic, name);
-  rename = pic_add_rename(pic, pic->lib->env, sym);
-  define_macro(pic, rename, macro, NULL);
+  define_macro(pic, id, pic_proc_new(pic, func, pic_symbol_name(pic, name)), NULL);
 
   /* auto export! */
-  pic_export(pic, sym);
+  pic_export(pic, name);
 }
 
 bool
@@ -554,15 +408,6 @@ pic_identifier_p(pic_state *pic, pic_value obj)
   return pic_sym_p(obj) && ! pic_interned_p(pic, pic_sym(obj));
 }
 
-bool
-pic_identifier_eq_p(pic_state *pic, struct pic_senv *e1, pic_sym x, struct pic_senv *e2, pic_sym y)
-{
-  x = make_identifier(pic, x, e1);
-  y = make_identifier(pic, y, e2);
-
-  return x == y;
-}
-
 static pic_value
 pic_macro_gensym(pic_state *pic)
 {
@@ -575,6 +420,16 @@ pic_macro_gensym(pic_state *pic)
   return pic_sym_value(uniq);
 }
 
+static pic_value
+pic_macro_ungensym(pic_state *pic)
+{
+  pic_sym sym;
+
+  pic_get_args(pic, "m", &sym);
+
+  return pic_sym_value(pic_ungensym(pic, sym));
+}
+
 static pic_value
 pic_macro_macroexpand(pic_state *pic)
 {
@@ -582,23 +437,32 @@ pic_macro_macroexpand(pic_state *pic)
 
   pic_get_args(pic, "o", &expr);
 
-  return pic_macroexpand(pic, expr);
+  return pic_macroexpand(pic, expr, pic->lib);
 }
 
 static pic_value
 pic_macro_macroexpand_1(pic_state *pic)
 {
-  pic_value expr, val;
+  struct pic_senv *senv = pic->lib->env;
+  struct pic_macro *mac;
+  pic_value expr;
+  pic_sym sym;
 
   pic_get_args(pic, "o", &expr);
 
-  val = macroexpand_one(pic, expr, pic->lib->env);
-  if (pic_undef_p(val)) {
-    return pic_values2(pic, expr, pic_false_value());
+  if (pic_sym_p(expr)) {
+    if (pic_interned_p(pic, pic_sym(expr))) {
+      return pic_values2(pic, macroexpand_symbol(pic, pic_sym(expr), senv), pic_true_value());
+    }
   }
-  else {
-    return pic_values2(pic, val, pic_true_value());
+  if (pic_pair_p(expr) && pic_sym_p(pic_car(pic, expr))) {
+    sym = make_identifier(pic, pic_sym(pic_car(pic, expr)), senv);
+    if ((mac = find_macro(pic, sym)) != NULL) {
+      return pic_values2(pic, macroexpand_macro(pic, mac, expr, senv), pic_true_value());
+    }
   }
+
+  return pic_values2(pic, expr, pic_false_value());     /* no expansion occurred */
 }
 
 static pic_value
@@ -611,27 +475,6 @@ pic_macro_identifier_p(pic_state *pic)
   return pic_bool_value(pic_identifier_p(pic, obj));
 }
 
-static pic_value
-pic_macro_identifier_eq_p(pic_state *pic)
-{
-  pic_sym x, y;
-  pic_value e, f;
-  struct pic_senv *e1, *e2;
-
-  pic_get_args(pic, "omom", &e, &x, &f, &y);
-
-  if (! pic_senv_p(e)) {
-    pic_error(pic, "unexpected type of argument 1");
-  }
-  e1 = pic_senv_ptr(e);
-  if (! pic_senv_p(f)) {
-    pic_error(pic, "unexpected type of argument 3");
-  }
-  e2 = pic_senv_ptr(f);
-
-  return pic_bool_value(pic_identifier_eq_p(pic, e1, x, e2, y));
-}
-
 static pic_value
 pic_macro_make_identifier(pic_state *pic)
 {
@@ -648,12 +491,12 @@ pic_macro_make_identifier(pic_state *pic)
 void
 pic_init_macro(pic_state *pic)
 {
-  pic_deflibrary ("(picrin macro)") {
+  pic_deflibrary (pic, "(picrin macro)") {
     pic_defun(pic, "gensym", pic_macro_gensym);
+    pic_defun(pic, "ungensym", pic_macro_ungensym);
     pic_defun(pic, "macroexpand", pic_macro_macroexpand);
     pic_defun(pic, "macroexpand-1", pic_macro_macroexpand_1);
     pic_defun(pic, "identifier?", pic_macro_identifier_p);
-    pic_defun(pic, "identifier=?", pic_macro_identifier_eq_p);
     pic_defun(pic, "make-identifier", pic_macro_make_identifier);
   }
 }
diff --git a/src/number.c b/src/number.c
index 8e15860a..ed6ce95c 100644
--- a/src/number.c
+++ b/src/number.c
@@ -28,6 +28,59 @@ lcm(int a, int b)
   return fabs((double)a * b) / gcd(a, b);
 }
 
+/**
+ * Returns the length of string representing val.
+ * radix is between 2 and 36 (inclusive).
+ * No error checks are performed in this function.
+ */
+static int
+number_string_length(int val, int radix)
+{
+  long long v = val; /* in case val == INT_MIN */
+  int count = 0;
+  if (val == 0) {
+    return 1;
+  }
+  if (val < 0) {
+    v = - v;
+    count = 1;
+  }
+  while (v > 0) {
+    ++count;
+    v /= radix;
+  }
+  return count;
+}
+
+/**
+ * Returns the string representing val.
+ * radix is between 2 and 36 (inclusive).
+ * This function overwrites buffer and stores the result.
+ * No error checks are performed in this function. It is caller's responsibility to avoid buffer-overrun.
+ */
+static void
+number_string(int val, int radix, int length, char *buffer) {
+  const char digits[37] = "0123456789abcdefghijklmnopqrstuvwxyz";
+  long long v = val;
+  int i;
+  if (val == 0) {
+    buffer[0] = '0';
+    buffer[1] = '\0';
+    return;
+  }
+  if (val < 0) {
+    buffer[0] = '-';
+    v = -v;
+  }
+
+  for(i = length - 1; v > 0; --i) {
+    buffer[i] = digits[v % radix];
+    v /= radix;
+  }
+  buffer[length] = '\0';
+  return;
+}
+
 static pic_value
 pic_number_real_p(pic_state *pic)
 {
@@ -748,10 +801,16 @@ pic_number_number_to_string(pic_state *pic)
 
   pic_get_args(pic, "F|i", &f, &e, &radix);
 
-  if (e) {
-    char buf[snprintf(NULL, 0, "%d", (int)f) + 1];
+  if (radix < 2 || radix > 36) {
+    pic_errorf(pic, "number->string: invalid radix %d (between 2 and 36, inclusive)", radix);
+  }
 
-    snprintf(buf, sizeof buf, "%d", (int)f);
+  if (e) {
+    int ival = (int) f;
+    int ilen = number_string_length(ival, radix);
+    char buf[ilen + 1];
+
+    number_string(ival, radix, ilen, buf);
 
     return pic_obj_value(pic_str_new(pic, buf, sizeof buf - 1));
   }
@@ -866,7 +925,7 @@ pic_init_number(pic_state *pic)
   pic_defun(pic, "string->number", pic_number_string_to_number);
   pic_gc_arena_restore(pic, ai);
 
-  pic_deflibrary ("(scheme inexact)") {
+  pic_deflibrary (pic, "(scheme inexact)") {
     pic_defun(pic, "finite?", pic_number_finite_p);
     pic_defun(pic, "infinite?", pic_number_infinite_p);
     pic_defun(pic, "nan?", pic_number_nan_p);
diff --git a/src/port.c b/src/port.c
index de01f62e..b9790d06 100644
--- a/src/port.c
+++ b/src/port.c
@@ -377,7 +377,7 @@ pic_port_get_output_bytevector(pic_state *pic)
 static pic_value
 pic_port_read_char(pic_state *pic)
 {
-  char c;
+  int c;
   struct pic_port *port = pic_stdin(pic);
 
   pic_get_args(pic, "|p", &port);
@@ -388,14 +388,14 @@ pic_port_read_char(pic_state *pic)
     return pic_eof_object();
   }
   else {
-    return pic_char_value(c);
+    return pic_char_value((char)c);
   }
 }
 
 static pic_value
 pic_port_peek_char(pic_state *pic)
 {
-  char c;
+  int c;
   struct pic_port *port = pic_stdin(pic);
 
   pic_get_args(pic, "|p", &port);
@@ -407,14 +407,14 @@ pic_port_peek_char(pic_state *pic)
   }
   else {
     xungetc(c, port->file);
-    return pic_char_value(c);
+    return pic_char_value((char)c);
   }
 }
 
 static pic_value
 pic_port_read_line(pic_state *pic)
 {
-  char c;
+  int c;
   struct pic_port *port = pic_stdin(pic), *buf;
   struct pic_string *str;
 
@@ -453,16 +453,16 @@ pic_port_read_string(pic_state *pic){
   struct pic_port *port = pic_stdin(pic), *buf;
   pic_str *str;
   int k, i;
-  char c;
+  int c;
 
   pic_get_args(pic, "i|p", &k,  &port);
 
   assert_port_profile(port, PIC_PORT_IN | PIC_PORT_TEXT, PIC_PORT_OPEN, "read-stritg");
 
+  c = EOF;
   buf = pic_open_output_string(pic);
   for(i = 0; i < k; ++i) {
-    c = xfgetc(port->file);
-    if( c == EOF){
+    if((c = xfgetc(port->file)) == EOF){
       break;
     }
     xfputc(c, buf->file);
@@ -481,7 +481,7 @@ pic_port_read_string(pic_state *pic){
 static pic_value
 pic_port_read_byte(pic_state *pic){
   struct pic_port *port = pic_stdin(pic);
-  char c;
+  int c;
   pic_get_args(pic, "|p", &port);
 
   assert_port_profile(port, PIC_PORT_IN | PIC_PORT_BINARY, PIC_PORT_OPEN, "read-u8");
@@ -495,14 +495,15 @@ pic_port_read_byte(pic_state *pic){
 static pic_value
 pic_port_peek_byte(pic_state *pic)
 {
-  char c;
+  int c;
   struct pic_port *port = pic_stdin(pic);
 
   pic_get_args(pic, "|p", &port);
 
   assert_port_profile(port, PIC_PORT_IN | PIC_PORT_BINARY, PIC_PORT_OPEN, "peek-u8");
 
-  if ((c = xfgetc(port->file)) == EOF) {
+  c = xfgetc(port->file);
+  if (c == EOF) {
     return pic_eof_object();
   }
   else {
@@ -695,7 +696,7 @@ pic_init_port(pic_state *pic)
   STDOUT = port_new_stdport(pic, xstdout, PIC_PORT_OUT);
   STDERR = port_new_stdport(pic, xstderr, PIC_PORT_OUT);
 
-  pic_deflibrary ("(picrin port)") {
+  pic_deflibrary (pic, "(picrin port)") {
     pic_define(pic, "standard-input-port", pic_obj_value(STDIN));
     pic_define(pic, "standard-output-port", pic_obj_value(STDOUT));
     pic_define(pic, "standard-error-port", pic_obj_value(STDERR));
diff --git a/src/proc.c b/src/proc.c
index 84967224..889a621d 100644
--- a/src/proc.c
+++ b/src/proc.c
@@ -177,7 +177,7 @@ pic_init_proc(pic_state *pic)
   pic_defun(pic, "map", pic_proc_map);
   pic_defun(pic, "for-each", pic_proc_for_each);
 
-  pic_deflibrary ("(picrin attribute)") {
+  pic_deflibrary (pic, "(picrin attribute)") {
     pic_defun(pic, "attribute", pic_proc_attribute);
   }
 }
diff --git a/src/read.c b/src/read.c
index d7726471..8c9621ee 100644
--- a/src/read.c
+++ b/src/read.c
@@ -13,10 +13,10 @@
 #include "picrin/blob.h"
 #include "picrin/port.h"
 
-typedef pic_value (*read_func_t)(pic_state *, struct pic_port *, char);
+typedef pic_value (*read_func_t)(pic_state *, struct pic_port *, int);
 
-static pic_value read(pic_state *pic, struct pic_port *port, char c);
-static pic_value read_nullable(pic_state *pic, struct pic_port *port, char c);
+static pic_value read(pic_state *pic, struct pic_port *port, int c);
+static pic_value read_nullable(pic_state *pic, struct pic_port *port, int c);
 
 static noreturn void
 read_error(pic_state *pic, const char *msg)
@@ -24,8 +24,8 @@ read_error(pic_state *pic, const char *msg)
   pic_throw(pic, PIC_ERROR_READ, msg, pic_nil_value());
 }
 
-static char
-skip(struct pic_port *port, char c)
+static int
+skip(struct pic_port *port, int c)
 {
   while (isspace(c)) {
     c = xfgetc(port->file);
@@ -33,16 +33,16 @@ skip(struct pic_port *port, char c)
   return c;
 }
 
-static char
+static int
 next(struct pic_port *port)
 {
   return xfgetc(port->file);
 }
 
-static char
+static int
 peek(struct pic_port *port)
 {
-  char c;
+  int c;
 
   xungetc((c = xfgetc(port->file)), port->file);
 
@@ -52,9 +52,9 @@ peek(struct pic_port *port)
 static bool
 expect(struct pic_port *port, const char *str)
 {
-  char c;
+  int c;
 
-  while ((c = *str++) != 0) {
+  while ((c = (int)*str++) != 0) {
     if (c != peek(port))
       return false;
     next(port);
@@ -64,13 +64,25 @@ expect(struct pic_port *port, const char *str)
 }
 
 static bool
-isdelim(char c)
+isdelim(int c)
 {
-  return c == EOF || strchr("();,|\" \t\n\r", c) != NULL; /* ignores "#", "'" */
+  return c == EOF || strchr("();,|\" \t\n\r", (char)c) != NULL; /* ignores "#", "'" */
+}
+
+static bool
+strcaseeq(const char *s1, const char *s2)
+{
+  char a, b;
+
+  while ((a = *s1++) * (b = *s2++)) {
+    if (tolower(a) != tolower(b))
+      return false;
+  }
+  return a == b;
 }
 
 static pic_value
-read_comment(pic_state *pic, struct pic_port *port, char c)
+read_comment(pic_state *pic, struct pic_port *port, int c)
 {
   UNUSED(pic);
 
@@ -82,9 +94,9 @@ read_comment(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_block_comment(pic_state *pic, struct pic_port *port, char c)
+read_block_comment(pic_state *pic, struct pic_port *port, int c)
 {
-  char x, y;
+  int x, y;
   int i = 1;
 
   UNUSED(pic);
@@ -107,7 +119,7 @@ read_block_comment(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_datum_comment(pic_state *pic, struct pic_port *port, char c)
+read_datum_comment(pic_state *pic, struct pic_port *port, int c)
 {
   UNUSED(c);
 
@@ -117,18 +129,18 @@ read_datum_comment(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_directive(pic_state *pic, struct pic_port *port, char c)
+read_directive(pic_state *pic, struct pic_port *port, int c)
 {
-  switch (peek(port)) {
+  switch ((char)peek(port)) {
   case 'n':
     if (expect(port, "no-fold-case")) {
-      /* :FIXME: set no-fold-case flag */
+      pic->rfcase = false;
       return pic_undef_value();
     }
     break;
   case 'f':
     if (expect(port, "fold-case")) {
-      /* :FIXME: set fold-case flag */
+      pic->rfcase = true;
       return pic_undef_value();
     }
     break;
@@ -138,7 +150,7 @@ read_directive(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_quote(pic_state *pic, struct pic_port *port, char c)
+read_quote(pic_state *pic, struct pic_port *port, int c)
 {
   UNUSED(c);
 
@@ -146,7 +158,7 @@ read_quote(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_quasiquote(pic_state *pic, struct pic_port *port, char c)
+read_quasiquote(pic_state *pic, struct pic_port *port, int c)
 {
   UNUSED(c);
 
@@ -154,11 +166,11 @@ read_quasiquote(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_comma(pic_state *pic, struct pic_port *port, char c)
+read_comma(pic_state *pic, struct pic_port *port, int c)
 {
   c = next(port);
 
-  if (c == '@') {
+  if ((char)c == '@') {
     return pic_list2(pic, pic_sym_value(pic->sUNQUOTE_SPLICING), read(pic, port, next(port)));
   } else {
     return pic_list2(pic, pic_sym_value(pic->sUNQUOTE), read(pic, port, c));
@@ -166,7 +178,7 @@ read_comma(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_symbol(pic_state *pic, struct pic_port *port, char c)
+read_symbol(pic_state *pic, struct pic_port *port, int c)
 {
   size_t len;
   char *buf;
@@ -179,20 +191,22 @@ read_symbol(pic_state *pic, struct pic_port *port, char c)
     if (len != 0) {
       c = next(port);
     }
+    if (pic->rfcase) {
+      c = tolower(c);
+    }
     len += 1;
     buf = pic_realloc(pic, buf, len + 1);
-    buf[len - 1] = c;
+    buf[len - 1] = (char)c;
   } while (! isdelim(peek(port)));
 
-  buf[len] = '\0';
-  sym = pic_intern_cstr(pic, buf);
+  sym = pic_intern(pic, buf, len);
   pic_free(pic, buf);
 
   return pic_sym_value(sym);
 }
 
 static size_t
-read_uinteger(pic_state *pic, struct pic_port *port, char c, char buf[])
+read_uinteger(pic_state *pic, struct pic_port *port, int c, char buf[])
 {
   size_t i = 0;
 
@@ -200,9 +214,9 @@ read_uinteger(pic_state *pic, struct pic_port *port, char c, char buf[])
     read_error(pic, "expected one or more digits");
   }
 
-  buf[i++] = c;
+  buf[i++] = (char)c;
   while (isdigit(c = peek(port))) {
-    buf[i++] = next(port);
+    buf[i++] = (char)next(port);
   }
 
   buf[i] = '\0';
@@ -211,7 +225,7 @@ read_uinteger(pic_state *pic, struct pic_port *port, char c, char buf[])
 }
 
 static pic_value
-read_number(pic_state *pic, struct pic_port *port, char c)
+read_number(pic_state *pic, struct pic_port *port, int c)
 {
   char buf[256];
   size_t i;
@@ -219,10 +233,10 @@ read_number(pic_state *pic, struct pic_port *port, char c)
 
   i = read_uinteger(pic, port, c, buf);
 
-  switch (peek(port)) {
+  switch ((char)peek(port)) {
   case '.':
     do {
-      buf[i++] = next(port);
+      buf[i++] = (char)next(port);
     } while (isdigit(peek(port)));
     buf[i] = '\0';
     return pic_float_value(atof(buf));
@@ -253,7 +267,7 @@ negate(pic_value n)
 }
 
 static pic_value
-read_minus(pic_state *pic, struct pic_port *port, char c)
+read_minus(pic_state *pic, struct pic_port *port, int c)
 {
   pic_value sym;
 
@@ -262,10 +276,10 @@ read_minus(pic_state *pic, struct pic_port *port, char c)
   }
   else {
     sym = read_symbol(pic, port, c);
-    if (pic_eq_p(sym, pic_sym_value(pic_intern_cstr(pic, "-inf.0")))) {
+    if (strcaseeq(pic_symbol_name(pic, pic_sym(sym)), "-inf.0")) {
       return pic_float_value(-INFINITY);
     }
-    if (pic_eq_p(sym, pic_sym_value(pic_intern_cstr(pic, "-nan.0")))) {
+    if (strcaseeq(pic_symbol_name(pic, pic_sym(sym)), "-nan.0")) {
       return pic_float_value(-NAN);
     }
     return sym;
@@ -273,7 +287,7 @@ read_minus(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_plus(pic_state *pic, struct pic_port *port, char c)
+read_plus(pic_state *pic, struct pic_port *port, int c)
 {
   pic_value sym;
 
@@ -282,10 +296,10 @@ read_plus(pic_state *pic, struct pic_port *port, char c)
   }
   else {
     sym = read_symbol(pic, port, c);
-    if (pic_eq_p(sym, pic_sym_value(pic_intern_cstr(pic, "+inf.0")))) {
+    if (strcaseeq(pic_symbol_name(pic, pic_sym(sym)), "+inf.0")) {
       return pic_float_value(INFINITY);
     }
-    if (pic_eq_p(sym, pic_sym_value(pic_intern_cstr(pic, "+nan.0")))) {
+    if (strcaseeq(pic_symbol_name(pic, pic_sym(sym)), "+nan.0")) {
       return pic_float_value(NAN);
     }
     return read_symbol(pic, port, c);
@@ -293,13 +307,13 @@ read_plus(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_boolean(pic_state *pic, struct pic_port *port, char c)
+read_boolean(pic_state *pic, struct pic_port *port, int c)
 {
   UNUSED(pic);
   UNUSED(port);
 
   if (! isdelim(peek(port))) {
-    if (c == 't') {
+    if ((char)c == 't') {
       if (! expect(port, "rue")) {
         goto fail;
       }
@@ -310,7 +324,7 @@ read_boolean(pic_state *pic, struct pic_port *port, char c)
     }
   }
 
-  if (c == 't') {
+  if ((char)c == 't') {
     return pic_true_value();
   } else {
     return pic_false_value();
@@ -321,12 +335,12 @@ read_boolean(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_char(pic_state *pic, struct pic_port *port, char c)
+read_char(pic_state *pic, struct pic_port *port, int c)
 {
   c = next(port);
 
   if (! isdelim(peek(port))) {
-    switch (c) {
+    switch ((char)c) {
     default: read_error(pic, "unexpected character after char literal");
     case 'a': c = '\a'; if (! expect(port, "lerm")) goto fail; break;
     case 'b': c = '\b'; if (! expect(port, "ackspace")) goto fail; break;
@@ -356,7 +370,7 @@ read_char(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_string(pic_state *pic, struct pic_port *port, char c)
+read_string(pic_state *pic, struct pic_port *port, int c)
 {
   char *buf;
   size_t size, cnt;
@@ -378,7 +392,7 @@ read_string(pic_state *pic, struct pic_port *port, char c)
       case 'r': c = '\r'; break;
       }
     }
-    buf[cnt++] = c;
+    buf[cnt++] = (char)c;
     if (cnt >= size) {
       buf = pic_realloc(pic, buf, size *= 2);
     }
@@ -405,7 +419,7 @@ read_pipe(pic_state *pic, struct pic_port *port, char c)
   cnt = 0;
   while ((c = next(port)) != '|') {
     if (c == '\\') {
-      switch (c = next(port)) {
+      switch ((char)(c = next(port))) {
       case 'a': c = '\a'; break;
       case 'b': c = '\b'; break;
       case 't': c = '\t'; break;
@@ -421,7 +435,7 @@ read_pipe(pic_state *pic, struct pic_port *port, char c)
         break;
       }
     }
-    buf[cnt++] = c;
+    buf[cnt++] = (char)c;
     if (cnt >= size) {
       buf = pic_realloc(pic, buf, size *= 2);
     }
@@ -435,7 +449,7 @@ read_pipe(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_unsigned_blob(pic_state *pic, struct pic_port *port, char c)
+read_unsigned_blob(pic_state *pic, struct pic_port *port, int c)
 {
   int nbits, n;
   size_t len, i;
@@ -481,7 +495,7 @@ read_unsigned_blob(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_pair(pic_state *pic, struct pic_port *port, char c)
+read_pair(pic_state *pic, struct pic_port *port, int c)
 {
   char tOPEN = c, tCLOSE = (tOPEN == '(') ? ')' : ']';
   pic_value car, cdr;
@@ -518,7 +532,7 @@ read_pair(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_vector(pic_state *pic, struct pic_port *port, char c)
+read_vector(pic_state *pic, struct pic_port *port, int c)
 {
   pic_value list;
 
@@ -531,9 +545,9 @@ static pic_value
 read_label_set(pic_state *pic, struct pic_port *port, int i)
 {
   pic_value val;
-  char c;
+  int c;
 
-  switch (c = skip(port, ' ')) {
+  switch ((char)(c = skip(port, ' '))) {
   case '(': case '[':
     {
       pic_value tmp;
@@ -600,7 +614,7 @@ read_label_ref(pic_state *pic, struct pic_port *port, int i)
 }
 
 static pic_value
-read_label(pic_state *pic, struct pic_port *port, char c)
+read_label(pic_state *pic, struct pic_port *port, int c)
 {
   int i;
 
@@ -619,11 +633,11 @@ read_label(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_dispatch(pic_state *pic, struct pic_port *port, char c)
+read_dispatch(pic_state *pic, struct pic_port *port, int c)
 {
   c = next(port);
 
-  switch (c) {
+  switch ((char)c) {
   case '!':
     return read_directive(pic, port, c);
   case '|':
@@ -647,7 +661,7 @@ read_dispatch(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read_nullable(pic_state *pic, struct pic_port *port, char c)
+read_nullable(pic_state *pic, struct pic_port *port, int c)
 {
   c = skip(port, c);
 
@@ -655,7 +669,9 @@ read_nullable(pic_state *pic, struct pic_port *port, char c)
     read_error(pic, "unexpected EOF");
   }
 
-  switch (c) {
+  switch ((char)c) {
+  case ')':
+    read_error(pic, "unmatched parenthesis");
   case ';':
     return read_comment(pic, port, c);
   case '#':
@@ -685,7 +701,7 @@ read_nullable(pic_state *pic, struct pic_port *port, char c)
 }
 
 static pic_value
-read(pic_state *pic, struct pic_port *port, char c)
+read(pic_state *pic, struct pic_port *port, int c)
 {
   pic_value val;
 
@@ -704,7 +720,7 @@ pic_value
 pic_read(pic_state *pic, struct pic_port *port)
 {
   pic_value val;
-  char c = next(port);
+  int c = next(port);
 
  retry:
   c = skip(port, c);
@@ -787,7 +803,7 @@ pic_read_read(pic_state *pic)
 void
 pic_init_read(pic_state *pic)
 {
-  pic_deflibrary ("(scheme read)") {
+  pic_deflibrary (pic, "(scheme read)") {
     pic_defun(pic, "read", pic_read_read);
   }
 }
diff --git a/src/record.c b/src/record.c
index f0028d65..0e9b026f 100644
--- a/src/record.c
+++ b/src/record.c
@@ -105,7 +105,7 @@ pic_record_record_set(pic_state *pic)
 void
 pic_init_record(pic_state *pic)
 {
-  pic_deflibrary ("(picrin record-primitive)") {
+  pic_deflibrary (pic, "(picrin record-primitive)") {
     pic_defun(pic, "make-record", pic_record_record);
     pic_defun(pic, "record-of?", pic_record_record_of);
     pic_defun(pic, "record-ref", pic_record_record_ref);
diff --git a/src/state.c b/src/state.c
index 758bae9c..6cd6c139 100644
--- a/src/state.c
+++ b/src/state.c
@@ -9,6 +9,7 @@
 #include "picrin/proc.h"
 #include "picrin/macro.h"
 #include "picrin/cont.h"
+#include "picrin/error.h"
 
 void pic_init_core(pic_state *);
 
@@ -22,18 +23,14 @@ pic_open(int argc, char *argv[], char **envp)
 
   pic = (pic_state *)malloc(sizeof(pic_state));
 
+  /* root block */
+  pic->blk = NULL;
+
   /* command line */
   pic->argc = argc;
   pic->argv = argv;
   pic->envp = envp;
 
-  /* root block */
-  pic->blk = (pic_block *)malloc(sizeof(pic_block));
-  pic->blk->prev = NULL;
-  pic->blk->depth = 0;
-  pic->blk->in = pic->blk->out = NULL;
-  pic->blk->refcnt = 1;
-
   /* prepare VM stack */
   pic->stbase = pic->sp = (pic_value *)calloc(PIC_STACK_SIZE, sizeof(pic_value));
   pic->stend = pic->stbase + PIC_STACK_SIZE;
@@ -52,25 +49,25 @@ pic_open(int argc, char *argv[], char **envp)
   pic->uniq_sym_cnt = 0;
 
   /* global variables */
-  xh_init_int(&pic->global_tbl, sizeof(size_t));
-  pic->globals = (pic_value *)calloc(PIC_GLOBALS_SIZE, sizeof(pic_value));
-  pic->glen = 0;
-  pic->gcapa = PIC_GLOBALS_SIZE;
+  xh_init_int(&pic->globals, sizeof(pic_value));
 
   /* macros */
   xh_init_int(&pic->macros, sizeof(struct pic_macro *));
 
   /* libraries */
-  pic->lib_tbl = pic_nil_value();
+  pic->libs = pic_nil_value();
   pic->lib = NULL;
 
   /* reader */
+  pic->rfcase = false;
   xh_init_int(&pic->rlabels, sizeof(pic_value));
 
   /* error handling */
   pic->jmp = NULL;
   pic->err = NULL;
-  pic->try_jmps = NULL;
+  pic->try_jmps = calloc(PIC_RESCUE_SIZE, sizeof(struct pic_jmpbuf));
+  pic->try_jmp_idx = 0;
+  pic->try_jmp_size = PIC_RESCUE_SIZE;
 
   /* GC arena */
   pic->arena = (struct pic_object **)calloc(PIC_ARENA_SIZE, sizeof(struct pic_object **));
@@ -132,6 +129,12 @@ pic_open(int argc, char *argv[], char **envp)
   register_renamed_symbol(pic, rEXPORT, "export");
   pic_gc_arena_restore(pic, ai);
 
+  /* root block */
+  pic->blk = (struct pic_block *)pic_obj_alloc(pic, sizeof(struct pic_block), PIC_TT_BLK);
+  pic->blk->prev = NULL;
+  pic->blk->depth = 0;
+  pic->blk->in = pic->blk->out = NULL;
+
   pic_init_core(pic);
 
   /* set library */
@@ -147,16 +150,20 @@ pic_close(pic_state *pic)
   xh_iter it;
 
   /* invoke exit handlers */
-  PIC_BLK_EXIT(pic);
+  while (pic->blk) {
+    if (pic->blk->out) {
+      pic_apply0(pic, pic->blk->out);
+    }
+    pic->blk = pic->blk->prev;
+  }
 
   /* clear out root objects */
   pic->sp = pic->stbase;
   pic->ci = pic->cibase;
   pic->arena_idx = 0;
   pic->err = NULL;
-  pic->glen = 0;
   xh_clear(&pic->macros);
-  pic->lib_tbl = pic_nil_value();
+  pic->libs = pic_nil_value();
 
   /* free all heap objects */
   pic_gc_run(pic);
@@ -169,9 +176,9 @@ pic_close(pic_state *pic)
   free(pic->cibase);
 
   /* free global stacks */
-  free(pic->globals);
+  free(pic->try_jmps);
   xh_destroy(&pic->syms);
-  xh_destroy(&pic->global_tbl);
+  xh_destroy(&pic->globals);
   xh_destroy(&pic->macros);
   xh_destroy(&pic->rlabels);
 
diff --git a/src/string.c b/src/string.c
index 73dba061..ab679f50 100644
--- a/src/string.c
+++ b/src/string.c
@@ -62,13 +62,13 @@ pic_strlen(pic_str *str)
 char
 pic_str_ref(pic_state *pic, pic_str *str, size_t i)
 {
-  char c;
+  int c;
 
   c = xr_at(str->rope, i);
   if (c == -1) {
     pic_errorf(pic, "index out of range %d", i);
   }
-  return c;
+  return (char)c;
 }
 
 static xrope *
diff --git a/src/symbol.c b/src/symbol.c
index 1ebbdc3d..10fd3822 100644
--- a/src/symbol.c
+++ b/src/symbol.c
@@ -20,13 +20,13 @@ pic_intern(pic_state *pic, const char *str, size_t len)
   cstr[len] = '\0';
   memcpy(cstr, str, len);
 
-  e = xh_get(&pic->syms, cstr);
+  e = xh_get_str(&pic->syms, cstr);
   if (e) {
     return xh_val(e, pic_sym);
   }
 
   id = pic->sym_cnt++;
-  xh_put(&pic->syms, cstr, &id);
+  xh_put_str(&pic->syms, cstr, &id);
   xh_put_int(&pic->sym_names, id, &cstr);
   return id;
 }
@@ -41,12 +41,18 @@ pic_sym
 pic_gensym(pic_state *pic, pic_sym base)
 {
   int uid = pic->uniq_sym_cnt++, len;
-  char *str;
+  char *str, mark;
   pic_sym uniq;
 
-  len = snprintf(NULL, 0, "%s@%d", pic_symbol_name(pic, base), uid);
+  if (pic_interned_p(pic, base)) {
+    mark = '@';
+  } else {
+    mark = '.';
+  }
+
+  len = snprintf(NULL, 0, "%s%c%d", pic_symbol_name(pic, base), mark, uid);
   str = pic_alloc(pic, len + 1);
-  sprintf(str, "%s@%d", pic_symbol_name(pic, base), uid);
+  sprintf(str, "%s%c%d", pic_symbol_name(pic, base), mark, uid);
 
   /* don't put the symbol to pic->syms to keep it uninterned */
   uniq = pic->sym_cnt++;
@@ -55,6 +61,22 @@ pic_gensym(pic_state *pic, pic_sym base)
   return uniq;
 }
 
+pic_sym
+pic_ungensym(pic_state *pic, pic_sym base)
+{
+  const char *name, *occr;
+
+  if (pic_interned_p(pic, base)) {
+    return base;
+  }
+
+  name = pic_symbol_name(pic, base);
+  if ((occr = strrchr(name, '@')) == NULL) {
+    pic_abort(pic, "logic flaw");
+  }
+  return pic_intern(pic, name, occr - name);
+}
+
 bool
 pic_interned_p(pic_state *pic, pic_sym sym)
 {
diff --git a/src/system.c b/src/system.c
index 73b27262..20203d27 100644
--- a/src/system.c
+++ b/src/system.c
@@ -24,7 +24,7 @@ pic_system_cmdline(pic_state *pic)
     pic_gc_arena_restore(pic, ai);
   }
 
-  return v;
+  return pic_reverse(pic, v);
 }
 
 static pic_value
@@ -47,7 +47,7 @@ pic_system_exit(pic_state *pic)
     }
   }
 
-  PIC_BLK_EXIT(pic);
+  pic_close(pic);
 
   exit(status);
 }
@@ -126,7 +126,7 @@ pic_system_getenvs(pic_state *pic)
 void
 pic_init_system(pic_state *pic)
 {
-  pic_deflibrary ("(scheme process-context)") {
+  pic_deflibrary (pic, "(scheme process-context)") {
     pic_defun(pic, "command-line", pic_system_cmdline);
     pic_defun(pic, "exit", pic_system_exit);
     pic_defun(pic, "emergency-exit", pic_system_emergency_exit);
diff --git a/src/time.c b/src/time.c
index 23234117..8e42dc8e 100644
--- a/src/time.c
+++ b/src/time.c
@@ -41,7 +41,7 @@ pic_jiffies_per_second(pic_state *pic)
 void
 pic_init_time(pic_state *pic)
 {
-  pic_deflibrary ("(scheme time)") {
+  pic_deflibrary (pic, "(scheme time)") {
     pic_defun(pic, "current-second", pic_current_second);
     pic_defun(pic, "current-jiffy", pic_current_jiffy);
     pic_defun(pic, "jiffies-per-second", pic_jiffies_per_second);
diff --git a/src/var.c b/src/var.c
index 2524350f..a5836797 100644
--- a/src/var.c
+++ b/src/var.c
@@ -124,7 +124,7 @@ pic_var_parameter_pop(pic_state *pic)
 void
 pic_init_var(pic_state *pic)
 {
-  pic_deflibrary ("(picrin parameter)") {
+  pic_deflibrary (pic, "(picrin parameter)") {
     pic_defun(pic, "make-parameter", pic_var_make_parameter);
     pic_defun(pic, "parameter-ref", pic_var_parameter_ref);
     pic_defun(pic, "parameter-set!", pic_var_parameter_set);
diff --git a/src/vm.c b/src/vm.c
index 2c1c1eeb..b958ce4d 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -52,6 +52,7 @@ pic_get_proc(pic_state *pic)
  *  l   lambda object
  *  p   port object
  *  d   dictionary object
+ *  e   error object
  *
  *  |  optional operator
  *  *  variable length operator
@@ -364,8 +365,25 @@ pic_get_args(pic_state *pic, const char *format, ...)
       }
       break;
     }
+    case 'e': {
+      struct pic_error **e;
+      pic_value v;
+
+      e = va_arg(ap, struct pic_error **);
+      if (i < argc) {
+        v = GET_OPERAND(pic,i);
+        if (pic_error_p(v)) {
+          *e = pic_error_ptr(v);
+        }
+        else {
+          pic_error(pic, "pic_get_args, expected error");
+        }
+        i++;
+      }
+      break;
+    }
     default:
-      pic_error(pic, "pic_get_args: invalid argument specifier given");
+      pic_errorf(pic, "pic_get_args: invalid argument specifier '%c' given", c);
     }
   }
   if ('*' == c) {
@@ -387,79 +405,38 @@ pic_get_args(pic_state *pic, const char *format, ...)
   return i - 1;
 }
 
-static size_t
-global_ref(pic_state *pic, const char *name)
-{
-  xh_entry *e;
-  pic_sym sym, rename;
-
-  sym = pic_intern_cstr(pic, name);
-  if (! pic_find_rename(pic, pic->lib->env, sym, &rename)) {
-    return SIZE_MAX;
-  }
-  if (! (e = xh_get_int(&pic->global_tbl, rename))) {
-    return SIZE_MAX;
-  }
-  return xh_val(e, size_t);
-}
-
-static size_t
-global_def(pic_state *pic, const char *name)
-{
-  pic_sym sym, rename;
-  size_t gidx;
-
-  sym = pic_intern_cstr(pic, name);
-  if ((gidx = global_ref(pic, name)) != SIZE_MAX) {
-    pic_warn(pic, "redefining global");
-    return gidx;
-  }
-
-  /* register to the senv */
-  rename = pic_add_rename(pic, pic->lib->env, sym);
-
-  /* register to the global table */
-  gidx = pic->glen++;
-  if (pic->glen >= pic->gcapa) {
-    pic_error(pic, "global table overflow");
-  }
-  xh_put_int(&pic->global_tbl, rename, &gidx);
-
-  return gidx;
-}
-
 void
 pic_define(pic_state *pic, const char *name, pic_value val)
 {
+  pic_sym sym, rename;
+
+  sym = pic_intern_cstr(pic, name);
+
+  if (! pic_find_rename(pic, pic->lib->env, sym, &rename)) {
+    rename = pic_add_rename(pic, pic->lib->env, sym);
+  } else {
+    pic_warn(pic, "redefining global");
+  }
+
   /* push to the global arena */
-  pic->globals[global_def(pic, name)] = val;
+  xh_put_int(&pic->globals, rename, &val);
 
   /* export! */
-  pic_export(pic, pic_intern_cstr(pic, name));
+  pic_export(pic, sym);
 }
 
 pic_value
 pic_ref(pic_state *pic, const char *name)
 {
-  size_t gid;
+  pic_sym sym, rename;
 
-  gid = global_ref(pic, name);
-  if (gid == SIZE_MAX) {
+  sym = pic_intern_cstr(pic, name);
+
+  if (! pic_find_rename(pic, pic->lib->env, sym, &rename)) {
     pic_errorf(pic, "symbol \"%s\" not defined", name);
   }
-  return pic->globals[gid];
-}
 
-void
-pic_set(pic_state *pic, const char *name, pic_value value)
-{
-  size_t gid;
-
-  gid = global_ref(pic, name);
-  if (gid == SIZE_MAX) {
-    pic_error(pic, "symbol not defined");
-  }
-  pic->globals[gid] = value;
+  return xh_val(xh_get_int(&pic->globals, rename), pic_value);
 }
 
 pic_value
@@ -495,20 +472,36 @@ vm_push_env(pic_state *pic)
 }
 
 static void
-vm_tear_off(pic_state *pic)
+vm_tear_off(pic_callinfo *ci)
 {
   struct pic_env *env;
   int i;
 
-  assert(pic->ci->env != NULL);
+  assert(ci->env != NULL);
 
-  env = pic->ci->env;
+  env = ci->env;
+
+  if (env->regs == env->storage) {
+    return;                     /* is torn off */
+  }
   for (i = 0; i < env->regc; ++i) {
     env->storage[i] = env->regs[i];
   }
   env->regs = env->storage;
 }
 
+void
+pic_vm_tear_off(pic_state *pic)
+{
+  pic_callinfo *ci;
+
+  for (ci = pic->ci; ci > pic->cibase; ci--) {
+    if (ci->env != NULL) {
+      vm_tear_off(ci);
+    }
+  }
+}
+
 pic_value
 pic_apply0(pic_state *pic, struct pic_proc *proc)
 {
@@ -659,11 +652,19 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
       NEXT;
     }
     CASE(OP_GREF) {
-      PUSH(pic->globals[c.u.i]);
+      xh_entry *e;
+
+      if ((e = xh_get_int(&pic->globals, c.u.i)) == NULL) {
+        pic_errorf(pic, "logic flaw; reference to uninitialized global variable: ~s", pic_symbol_name(pic, c.u.i));
+      }
+      PUSH(xh_val(e, pic_value));
       NEXT;
     }
     CASE(OP_GSET) {
-      pic->globals[c.u.i] = POP();
+      pic_value val;
+
+      val = POP();
+      xh_put_int(&pic->globals, c.u.i, &val);
       NEXT;
     }
     CASE(OP_LREF) {
@@ -828,7 +829,7 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
       pic_callinfo *ci;
 
       if (pic->ci->env != NULL) {
-        vm_tear_off(pic);
+        vm_tear_off(pic->ci);
       }
 
       if (c.u.i == -1) {
@@ -854,7 +855,7 @@ pic_apply(pic_state *pic, struct pic_proc *proc, pic_value argv)
       pic_callinfo *ci;
 
       if (pic->ci->env != NULL) {
-        vm_tear_off(pic);
+        vm_tear_off(pic->ci);
       }
 
       pic->ci->retc = c.u.i;
@@ -1045,13 +1046,3 @@ pic_apply_trampoline(pic_state *pic, struct pic_proc *proc, pic_value args)
   ci->retc = pic_length(pic, args);
   return pic_obj_value(proc);
 }
-
-pic_value
-pic_eval(pic_state *pic, pic_value program)
-{
-  struct pic_proc *proc;
-
-  proc = pic_compile(pic, program);
-
-  return pic_apply(pic, proc, pic_nil_value());
-}
diff --git a/src/write.c b/src/write.c
index d776eaa0..bd13ac44 100644
--- a/src/write.c
+++ b/src/write.c
@@ -2,6 +2,8 @@
  * See Copyright Notice in picrin.h
  */
 
+#include <math.h>
+
 #include "picrin.h"
 #include "picrin/port.h"
 #include "picrin/pair.h"
@@ -54,29 +56,22 @@ struct writer_control {
 #define WRITE_MODE 1
 #define DISPLAY_MODE 2
 
-static struct writer_control *
-writer_control_new(pic_state *pic, xFILE *file, int mode)
+static void
+writer_control_init(struct writer_control *p, pic_state *pic, xFILE *file, int mode)
 {
-  struct writer_control *p;
-
-  p = (struct writer_control *)pic_alloc(pic, sizeof(struct writer_control));
   p->pic = pic;
   p->file = file;
   p->mode = mode;
   p->cnt = 0;
   xh_init_ptr(&p->labels, sizeof(int));
   xh_init_ptr(&p->visited, sizeof(int));
-  return p;
 }
 
 static void
 writer_control_destroy(struct writer_control *p)
 {
-  pic_state *pic = p->pic;
-
   xh_destroy(&p->labels);
   xh_destroy(&p->visited);
-  pic_free(pic, p);
 }
 
 static void
@@ -89,14 +84,14 @@ traverse_shared(struct writer_control *p, pic_value obj)
   switch (pic_type(obj)) {
   case PIC_TT_PAIR:
   case PIC_TT_VECTOR:
-    e = xh_get(&p->labels, pic_obj_ptr(obj));
+    e = xh_get_ptr(&p->labels, pic_obj_ptr(obj));
     if (e == NULL) {
       c = -1;
-      xh_put(&p->labels, pic_obj_ptr(obj), &c);
+      xh_put_ptr(&p->labels, pic_obj_ptr(obj), &c);
     }
     else if (xh_val(e, int) == -1) {
       c = p->cnt++;
-      xh_put(&p->labels, pic_obj_ptr(obj), &c);
+      xh_put_ptr(&p->labels, pic_obj_ptr(obj), &c);
       break;
     }
     else {
@@ -135,17 +130,17 @@ write_pair(struct writer_control *p, struct pic_pair *pair)
   else if (pic_pair_p(pair->cdr)) {
 
     /* shared objects */
-    if ((e = xh_get(&p->labels, pic_obj_ptr(pair->cdr))) && xh_val(e, int) != -1) {
+    if ((e = xh_get_ptr(&p->labels, pic_obj_ptr(pair->cdr))) && xh_val(e, int) != -1) {
       xfprintf(p->file, " . ");
 
-      if ((xh_get(&p->visited, pic_obj_ptr(pair->cdr)))) {
+      if ((xh_get_ptr(&p->visited, pic_obj_ptr(pair->cdr)))) {
         xfprintf(p->file, "#%d#", xh_val(e, int));
         return;
       }
       else {
         xfprintf(p->file, "#%d=", xh_val(e, int));
         c = 1;
-        xh_put(&p->visited, pic_obj_ptr(pair->cdr), &c);
+        xh_put_ptr(&p->visited, pic_obj_ptr(pair->cdr), &c);
       }
     }
     else {
@@ -185,19 +180,20 @@ write_core(struct writer_control *p, pic_value obj)
   size_t i;
   xh_entry *e;
   int c;
+  float f;
 
   /* shared objects */
   if (pic_vtype(obj) == PIC_VTYPE_HEAP
-      && (e = xh_get(&p->labels, pic_obj_ptr(obj)))
+      && (e = xh_get_ptr(&p->labels, pic_obj_ptr(obj)))
       && xh_val(e, int) != -1) {
-    if ((xh_get(&p->visited, pic_obj_ptr(obj)))) {
+    if ((xh_get_ptr(&p->visited, pic_obj_ptr(obj)))) {
       xfprintf(file, "#%d#", xh_val(e, int));
       return;
     }
     else {
       xfprintf(file, "#%d=", xh_val(e, int));
       c = 1;
-      xh_put(&p->visited, pic_obj_ptr(obj), &c);
+      xh_put_ptr(&p->visited, pic_obj_ptr(obj), &c);
     }
   }
 
@@ -257,7 +253,14 @@ write_core(struct writer_control *p, pic_value obj)
     }
     break;
   case PIC_TT_FLOAT:
-    xfprintf(file, "%f", pic_float(obj));
+    f = pic_float(obj);
+    if (isnan(f)) {
+      xfprintf(file, signbit(f) ? "-nan.0" : "+nan.0");
+    } else if (isinf(f)) {
+      xfprintf(file, signbit(f) ? "-inf.0" : "+inf.0");
+    } else {
+      xfprintf(file, "%f", pic_float(obj));
+    }
     break;
   case PIC_TT_INT:
     xfprintf(file, "%d", pic_int(obj));
@@ -303,95 +306,65 @@ write_core(struct writer_control *p, pic_value obj)
     }
     xfprintf(file, ")");
     break;
-  case PIC_TT_ERROR:
-    xfprintf(file, "#<error %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_ENV:
-    xfprintf(file, "#<env %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_CONT:
-    xfprintf(file, "#<cont %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_SENV:
-    xfprintf(file, "#<senv %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_MACRO:
-    xfprintf(file, "#<macro %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_LIB:
-    xfprintf(file, "#<lib %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_VAR:
-    xfprintf(file, "#<var %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_IREP:
-    xfprintf(file, "#<irep %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_DATA:
-    xfprintf(file, "#<data %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_DICT:
-    xfprintf(file, "#<dict %p>", pic_ptr(obj));
-    break;
-  case PIC_TT_RECORD:
-    xfprintf(file, "#<record %p>", pic_ptr(obj));
+  default:
+    xfprintf(file, "#<%s %p>", pic_type_repr(pic_type(obj)), pic_ptr(obj));
   }
 }
 
 static void
 write(pic_state *pic, pic_value obj, xFILE *file)
 {
-  struct writer_control *p;
+  struct writer_control p;
 
-  p = writer_control_new(pic, file, WRITE_MODE);
+  writer_control_init(&p, pic, file, WRITE_MODE);
 
-  traverse_shared(p, obj);      /* FIXME */
+  traverse_shared(&p, obj);      /* FIXME */
 
-  write_core(p, obj);
+  write_core(&p, obj);
 
-  writer_control_destroy(p);
+  writer_control_destroy(&p);
 }
 
 static void
 write_simple(pic_state *pic, pic_value obj, xFILE *file)
 {
-  struct writer_control *p;
+  struct writer_control p;
 
-  p = writer_control_new(pic, file, WRITE_MODE);
+  writer_control_init(&p, pic, file, WRITE_MODE);
 
   /* no traverse here! */
 
-  write_core(p, obj);
+  write_core(&p, obj);
 
-  writer_control_destroy(p);
+  writer_control_destroy(&p);
 }
 
 static void
 write_shared(pic_state *pic, pic_value obj, xFILE *file)
 {
-  struct writer_control *p;
+  struct writer_control p;
 
-  p = writer_control_new(pic, file, WRITE_MODE);
+  writer_control_init(&p, pic, file, WRITE_MODE);
 
-  traverse_shared(p, obj);
+  traverse_shared(&p, obj);
 
-  write_core(p, obj);
+  write_core(&p, obj);
 
-  writer_control_destroy(p);
+  writer_control_destroy(&p);
 }
 
 static void
 display(pic_state *pic, pic_value obj, xFILE *file)
 {
-  struct writer_control *p;
+  struct writer_control p;
 
-  p = writer_control_new(pic, file, DISPLAY_MODE);
+  writer_control_init(&p, pic, file, DISPLAY_MODE);
 
-  traverse_shared(p, obj);      /* FIXME */
+  traverse_shared(&p, obj);      /* FIXME */
 
-  write_core(p, obj);
+  write_core(&p, obj);
 
-  writer_control_destroy(p);
+  writer_control_destroy(&p);
 }
 
 pic_value
@@ -485,7 +458,7 @@ pic_write_display(pic_state *pic)
 void
 pic_init_write(pic_state *pic)
 {
-  pic_deflibrary ("(scheme write)") {
+  pic_deflibrary (pic, "(scheme write)") {
     pic_defun(pic, "write", pic_write_write);
     pic_defun(pic, "write-simple", pic_write_write_simple);
     pic_defun(pic, "write-shared", pic_write_write_shared);
diff --git a/t/r7rs-tests.scm b/t/r7rs-tests.scm
index c02b0c9d..19050d71 100644
--- a/t/r7rs-tests.scm
+++ b/t/r7rs-tests.scm
@@ -34,7 +34,7 @@
         (scheme file)
         (scheme read)
         (scheme write)
-;        (scheme eval)
+        (scheme eval)
         (scheme process-context)
         (scheme case-lambda)
         (picrin test))
@@ -212,33 +212,33 @@
 (let*-values (((root rem) (exact-integer-sqrt 32)))
   (test 35 (* root rem)))
 
-(test '(1073741824 0)
-    (let*-values (((root rem) (exact-integer-sqrt (expt 2 60))))
-      (list root rem)))
+;; (test '(1073741824 0)
+;;     (let*-values (((root rem) (exact-integer-sqrt (expt 2 60))))
+;;       (list root rem)))
 
-(test '(1518500249 3000631951)
-    (let*-values (((root rem) (exact-integer-sqrt (expt 2 61))))
-      (list root rem)))
+;; (test '(1518500249 3000631951)
+;;     (let*-values (((root rem) (exact-integer-sqrt (expt 2 61))))
+;;       (list root rem)))
 
-(test '(815238614083298888 443242361398135744)
-    (let*-values (((root rem) (exact-integer-sqrt (expt 2 119))))
-      (list root rem)))
+;; (test '(815238614083298888 443242361398135744)
+;;     (let*-values (((root rem) (exact-integer-sqrt (expt 2 119))))
+;;       (list root rem)))
 
-(test '(1152921504606846976 0)
-    (let*-values (((root rem) (exact-integer-sqrt (expt 2 120))))
-      (list root rem)))
+;; (test '(1152921504606846976 0)
+;;     (let*-values (((root rem) (exact-integer-sqrt (expt 2 120))))
+;;       (list root rem)))
 
-(test '(1630477228166597776 1772969445592542976)
-    (let*-values (((root rem) (exact-integer-sqrt (expt 2 121))))
-      (list root rem)))
+;; (test '(1630477228166597776 1772969445592542976)
+;;     (let*-values (((root rem) (exact-integer-sqrt (expt 2 121))))
+;;       (list root rem)))
 
-(test '(31622776601683793319 62545769258890964239)
-    (let*-values (((root rem) (exact-integer-sqrt (expt 10 39))))
-      (list root rem)))
+;; (test '(31622776601683793319 62545769258890964239)
+;;     (let*-values (((root rem) (exact-integer-sqrt (expt 10 39))))
+;;       (list root rem)))
 
-(let*-values (((root rem) (exact-integer-sqrt (expt 2 140))))
-  (test 0 rem)
-  (test (expt 2 140) (square root)))
+;; (let*-values (((root rem) (exact-integer-sqrt (expt 2 140))))
+;;   (test 0 rem)
+;;   (test (expt 2 140) (square root)))
 
 (test '(x y x y) (let ((a 'a) (b 'b) (x 'x) (y 'y))
   (let*-values (((a b) (values x y))
@@ -630,7 +630,7 @@
 ;; (test #f (real? -2.5+0.0i))
 ;; (test #t (real? #e1e10))
 (test #t (real? +inf.0))
-(test #f (rational? -inf.0))
+;; (test #f (rational? -inf.0))
 (test #t (rational? 6/10))
 (test #t (rational? 6/3))
 ;; (test #t (integer? 3+0i))
@@ -831,7 +831,7 @@
 (test 1.0 (inexact (cos 0))) ;; may return exact number
 (test -1.0 (cos 3.14159265358979))
 (test 0.0 (inexact (tan 0))) ;; may return exact number
-(test 1.5574077246549020703 (tan 1))
+(test 1.557407724654902292371616567834 (tan 1))
 
 (test 0.0 (asin 0))
 (test 1.5707963267948965580 (asin 1))
@@ -1596,7 +1596,6 @@
 
 (test -1 (call-with-values * -))
 
-#;
 (test '(connect talk1 disconnect
                 connect talk2 disconnect)
       (let ((path '())
@@ -1619,29 +1618,29 @@
 
 (test-begin "6.11 Exceptions")
 
-;; (test 65
-;;     (with-exception-handler
-;;      (lambda (con) 42)
-;;      (lambda ()
-;;        (+ (raise-continuable "should be a number")
-;;           23))))
+(test 65
+    (with-exception-handler
+     (lambda (con) 42)
+     (lambda ()
+       (+ (raise-continuable "should be a number")
+          23))))
 
-;; (test #t
-;;     (error-object? (guard (exn (else exn)) (error "BOOM!" 1 2 3))))
-;; (test "BOOM!"
-;;     (error-object-message (guard (exn (else exn)) (error "BOOM!" 1 2 3))))
-;; (test '(1 2 3)
-;;     (error-object-irritants (guard (exn (else exn)) (error "BOOM!" 1 2 3))))
+(test #t
+    (error-object? (guard (exn (else exn)) (error "BOOM!" 1 2 3))))
+(test "BOOM!"
+    (error-object-message (guard (exn (else exn)) (error "BOOM!" 1 2 3))))
+(test '(1 2 3)
+    (error-object-irritants (guard (exn (else exn)) (error "BOOM!" 1 2 3))))
 
-;; (test #f
-;;     (file-error? (guard (exn (else exn)) (error "BOOM!"))))
-;; (test #t
-;;     (file-error? (guard (exn (else exn)) (open-input-file " no such file "))))
+(test #f
+    (file-error? (guard (exn (else exn)) (error "BOOM!"))))
+(test #t
+    (file-error? (guard (exn (else exn)) (open-input-file " no such file "))))
 
-;; (test #f
-;;     (read-error? (guard (exn (else exn)) (error "BOOM!"))))
-;; (test #t
-;;     (read-error? (guard (exn (else exn)) (read (open-input-string ")")))))
+(test #f
+    (read-error? (guard (exn (else exn)) (error "BOOM!"))))
+(test #t
+    (read-error? (guard (exn (else exn)) (read (open-input-string ")")))))
 
 (define something-went-wrong #f)
 (define (test-exception-handler-1 v)
@@ -1659,126 +1658,126 @@
 (test '("condition: " an-error) something-went-wrong)
 
 (set! something-went-wrong #f)
-;; (define (test-exception-handler-2 v)
-;;   (guard (ex (else 'caught-another-exception))
-;;     (with-exception-handler
-;;      (lambda (x)
-;;        (set! something-went-wrong #t)
-;;        (list "exception:" x))
-;;      (lambda ()
-;;        (+ 1 (if (> v 0) (+ v 100) (raise 'an-error)))))))
-;; (test 106 (test-exception-handler-2 5))
-;; (test #f something-went-wrong)
-;; (test 'caught-another-exception (test-exception-handler-2 -1))
-;; (test #t something-went-wrong)
+(define (test-exception-handler-2 v)
+  (guard (ex (else 'caught-another-exception))
+    (with-exception-handler
+     (lambda (x)
+       (set! something-went-wrong #t)
+       (list "exception:" x))
+     (lambda ()
+       (+ 1 (if (> v 0) (+ v 100) (raise 'an-error)))))))
+(test 106 (test-exception-handler-2 5))
+(test #f something-went-wrong)
+(test 'caught-another-exception (test-exception-handler-2 -1))
+(test #t something-went-wrong)
 
 ;; Based on an example from R6RS-lib section 7.1 Exceptions.
 ;; R7RS section 6.11 Exceptions has a simplified version.
-;; (let* ((out (open-output-string))
-;;        (value (with-exception-handler
-;;                (lambda (con)
-;;                  (cond
-;;                   ((not (list? con))
-;;                    (raise con))
-;;                   ((list? con)
-;;                    (display (car con) out))
-;;                   (else
-;;                    (display "a warning has been issued" out)))
-;;                  42)
-;;                (lambda ()
-;;                  (+ (raise-continuable
-;;                      (list "should be a number"))
-;;                     23)))))
-;;   (test "should be a number" (get-output-string out))
-;;   (test 65 value))
+(let* ((out (open-output-string))
+       (value (with-exception-handler
+               (lambda (con)
+                 (cond
+                  ((not (list? con))
+                   (raise con))
+                  ((list? con)
+                   (display (car con) out))
+                  (else
+                   (display "a warning has been issued" out)))
+                 42)
+               (lambda ()
+                 (+ (raise-continuable
+                     (list "should be a number"))
+                    23)))))
+  (test "should be a number" (get-output-string out))
+  (test 65 value))
 
 ;; From SRFI-34 "Examples" section - #3
-;; (define (test-exception-handler-3 v out)
-;;   (guard (condition
-;;           (else
-;;            (display "condition: " out)
-;;            (write condition out)
-;;            (display #\! out)
-;;            'exception))
-;;          (+ 1 (if (= v 0) (raise 'an-error) (/ 10 v)))))
-;; (let* ((out (open-output-string))
-;;        (value (test-exception-handler-3 0 out)))
-;;   (test 'exception value)
-;;   (test "condition: an-error!" (get-output-string out)))
+(define (test-exception-handler-3 v out)
+  (guard (condition
+          (else
+           (display "condition: " out)
+           (write condition out)
+           (display #\! out)
+           'exception))
+         (+ 1 (if (= v 0) (raise 'an-error) (/ 10 v)))))
+(let* ((out (open-output-string))
+       (value (test-exception-handler-3 0 out)))
+  (test 'exception value)
+  (test "condition: an-error!" (get-output-string out)))
 
-;; (define (test-exception-handler-4 v out)
-;;   (call-with-current-continuation
-;;    (lambda (k)
-;;      (with-exception-handler
-;;       (lambda (x)
-;;         (display "reraised " out)
-;;         (write x out) (display #\! out)
-;;         (k 'zero))
-;;       (lambda ()
-;;         (guard (condition
-;;                 ((positive? condition)
-;;                  'positive)
-;;                 ((negative? condition)
-;;                  'negative))
-;;           (raise v)))))))
+(define (test-exception-handler-4 v out)
+  (call-with-current-continuation
+   (lambda (k)
+     (with-exception-handler
+      (lambda (x)
+        (display "reraised " out)
+        (write x out) (display #\! out)
+        (k 'zero))
+      (lambda ()
+        (guard (condition
+                ((positive? condition)
+                 'positive)
+                ((negative? condition)
+                 'negative))
+          (raise v)))))))
 
 ;; From SRFI-34 "Examples" section - #5
-;; (let* ((out (open-output-string))
-;;        (value (test-exception-handler-4 1 out)))
-;;   (test "" (get-output-string out))
-;;   (test 'positive value))
-;; ;; From SRFI-34 "Examples" section - #6
-;; (let* ((out (open-output-string))
-;;        (value (test-exception-handler-4 -1 out)))
-;;   (test "" (get-output-string out))
-;;   (test 'negative value))
-;; ;; From SRFI-34 "Examples" section - #7
-;; (let* ((out (open-output-string))
-;;        (value (test-exception-handler-4 0 out)))
-;;   (test "reraised 0!" (get-output-string out))
-;;   (test 'zero value))
+(let* ((out (open-output-string))
+       (value (test-exception-handler-4 1 out)))
+  (test "" (get-output-string out))
+  (test 'positive value))
+;; From SRFI-34 "Examples" section - #6
+(let* ((out (open-output-string))
+       (value (test-exception-handler-4 -1 out)))
+  (test "" (get-output-string out))
+  (test 'negative value))
+;; From SRFI-34 "Examples" section - #7
+(let* ((out (open-output-string))
+       (value (test-exception-handler-4 0 out)))
+  (test "reraised 0!" (get-output-string out))
+  (test 'zero value))
 
 ;; From SRFI-34 "Examples" section - #8
-;; (test 42
-;;     (guard (condition
-;;             ((assq 'a condition) => cdr)
-;;             ((assq 'b condition)))
-;;       (raise (list (cons 'a 42)))))
+(test 42
+    (guard (condition
+            ((assq 'a condition) => cdr)
+            ((assq 'b condition)))
+      (raise (list (cons 'a 42)))))
 
-;; ;; From SRFI-34 "Examples" section - #9
-;; (test '(b . 23)
-;;     (guard (condition
-;;             ((assq 'a condition) => cdr)
-;;             ((assq 'b condition)))
-;;       (raise (list (cons 'b 23)))))
+;; From SRFI-34 "Examples" section - #9
+(test '(b . 23)
+    (guard (condition
+            ((assq 'a condition) => cdr)
+            ((assq 'b condition)))
+      (raise (list (cons 'b 23)))))
 
-;; (test 'caught-d
-;;     (guard (condition
-;;             ((assq 'c condition) 'caught-c)
-;;             ((assq 'd condition) 'caught-d))
-;;       (list
-;;        (sqrt 8)
-;;        (guard (condition
-;;                ((assq 'a condition) => cdr)
-;;                ((assq 'b condition)))
-;;          (raise (list (cons 'd 24)))))))
+(test 'caught-d
+    (guard (condition
+            ((assq 'c condition) 'caught-c)
+            ((assq 'd condition) 'caught-d))
+      (list
+       (sqrt 8)
+       (guard (condition
+               ((assq 'a condition) => cdr)
+               ((assq 'b condition)))
+         (raise (list (cons 'd 24)))))))
 
 (test-end)
 
 (test-begin "6.12 Environments and evaluation")
 
-;; (test 21 (eval '(* 7 3) (scheme-report-environment 5)))
+(test 21 (eval '(* 7 3) (scheme-report-environment 5)))
 
-;; (test 20
-;;     (let ((f (eval '(lambda (f x) (f x x)) (null-environment 5))))
-;;       (f + 10)))
+(test 20
+    (let ((f (eval '(lambda (f x) (f x x)) (null-environment 5))))
+      (f + 10)))
 
-;; (test 1024 (eval '(expt 2 10) (environment '(scheme base))))
-;; ;; (sin 0) may return exact number
-;; (test 0.0 (inexact (eval '(sin 0) (environment '(scheme inexact)))))
-;; ;; ditto
-;; (test 1024.0 (eval '(+ (expt 2 10) (inexact (sin 0)))
-;;                    (environment '(scheme base) '(scheme inexact))))
+(test 1024 (eval '(expt 2 10) (environment '(scheme base))))
+;; (sin 0) may return exact number
+(test 0.0 (inexact (eval '(sin 0) (environment '(scheme inexact)))))
+;; ditto
+(test 1024.0 (eval '(+ (expt 2 10) (inexact (sin 0)))
+                   (environment '(scheme base) '(scheme inexact))))
 
 (test-end)
 
@@ -2013,7 +2012,7 @@
 (test 'Hello (read (open-input-string "|H\\x65;llo|")))
 
 (test 'abc (read (open-input-string "#!fold-case ABC")))
-(test 'ABC (read (open-input-string "#!fold-case #!no-fold-case ABC")))
+(test '|ABC| (read (open-input-string "#!fold-case #!no-fold-case ABC")))
 
 (test 'def (read (open-input-string "#; abc def")))
 (test 'def (read (open-input-string "; abc \ndef")))
@@ -2026,6 +2025,12 @@
 (test '(a . c) (read (open-input-string "(a . #;b c)")))
 (test '(a . b) (read (open-input-string "(a . b #;c)")))
 
+;; (define (test-read-error str)
+;;   (test #t
+;;       (guard (exn (else #t))
+;;         (read (open-input-string str))
+;;         #f)))
+
 ;; (test-read-error "(#;a . b)")
 ;; (test-read-error "(a . #;b)")
 ;; (test-read-error "(a #;. b)")
@@ -2069,6 +2074,15 @@
 
 (test-begin "Numeric syntax")
 
+(define-syntax test-numeric-syntax
+  (syntax-rules ()
+    ((test-numeric-syntax str expect strs ...)
+     (let* ((z (read (open-input-string str)))
+            (out (open-output-string))
+            (z-str (begin (write z out) (get-output-string out))))
+       (test expect (values z))
+       (test #t (and (member z-str '(str strs ...)) #t))))))
+
 ;; Simple
 (test-numeric-syntax "1" 1)
 ;; (test-numeric-syntax "+1" 1 "1")
@@ -2077,13 +2091,13 @@
 ;; (test-numeric-syntax "#I1" 1.0 "1.0" "1.")
 ;; (test-numeric-syntax "#i-1" -1.0 "-1.0" "-1.")
 ;; ;; Decimal
-(test-numeric-syntax "1.0" 1.0 "1.0" "1.")
-(test-numeric-syntax "1." 1.0 "1.0" "1.")
-(test-numeric-syntax ".1" 0.1 "0.1" "100.0e-3")
-(test-numeric-syntax "-.1" -0.1 "-0.1" "-100.0e-3")
+;; (test-numeric-syntax "1.0" 1.0 "1.0" "1.")
+;; (test-numeric-syntax "1." 1.0 "1.0" "1.")
+;; (test-numeric-syntax ".1" 0.1 "0.1" "100.0e-3")
+;; (test-numeric-syntax "-.1" -0.1 "-0.1" "-100.0e-3")
 ;; ;; Some Schemes don't allow negative zero. This is okay with the standard
-(test-numeric-syntax "-.0" -0.0 "-0." "-0.0" "0.0" "0." ".0")
-(test-numeric-syntax "-0." -0.0 "-.0" "-0.0" "0.0" "0." ".0")
+;; (test-numeric-syntax "-.0" -0.0 "-0." "-0.0" "0.0" "0." ".0")
+;; (test-numeric-syntax "-0." -0.0 "-.0" "-0.0" "0.0" "0." ".0")
 ;; (test-numeric-syntax "#i1.0" 1.0 "1.0" "1.")
 ;; (test-numeric-syntax "#e1.0" 1 "1")
 ;; (test-numeric-syntax "#e-.0" 0 "0")
@@ -2100,8 +2114,8 @@
 ;; (test-numeric-syntax "1l2" 100.0 "100.0" "100.")
 ;; (test-numeric-syntax "1L2" 100.0 "100.0" "100.")
 ;; ;; NaN, Inf
-(test-numeric-syntax "+nan.0" +nan.0 "+nan.0" "+NaN.0")
-(test-numeric-syntax "+NAN.0" +nan.0 "+nan.0" "+NaN.0")
+;; (test-numeric-syntax "+nan.0" +nan.0 "+nan.0" "+NaN.0")
+;; (test-numeric-syntax "+NAN.0" +nan.0 "+nan.0" "+NaN.0")
 (test-numeric-syntax "+inf.0" +inf.0 "+inf.0" "+Inf.0")
 (test-numeric-syntax "+InF.0" +inf.0 "+inf.0" "+Inf.0")
 (test-numeric-syntax "-inf.0" -inf.0 "-inf.0" "-Inf.0")
@@ -2110,10 +2124,10 @@
 ;; (test-numeric-syntax "#i+inf.0" +inf.0 "+inf.0" "+Inf.0")
 ;; (test-numeric-syntax "#i-inf.0" -inf.0 "-inf.0" "-Inf.0")
 ;; ;; Exact ratios
-(test-numeric-syntax "1/2" (/ 1 2))
+;; (test-numeric-syntax "1/2" (/ 1 2))
 ;; (test-numeric-syntax "#e1/2" (/ 1 2) "1/2")
 (test-numeric-syntax "10/2" 5 "5")
-(test-numeric-syntax "-1/2" (- (/ 1 2)))
+;; (test-numeric-syntax "-1/2" (- (/ 1 2)))
 (test-numeric-syntax "0/10" 0 "0")
 ;; (test-numeric-syntax "#e0/10" 0 "0")
 ;; (test-numeric-syntax "#i3/2" (/ 3.0 2.0) "1.5")
diff --git a/t/renaming-import.scm b/t/renaming-import.scm
new file mode 100644
index 00000000..628e3df4
--- /dev/null
+++ b/t/renaming-import.scm
@@ -0,0 +1,11 @@
+(define-library (foo)
+  (import (except (rename (prefix (only (scheme base) car cdr cons) my-)
+                          (my-car my-kar)
+                          (my-cdr my-kdr))
+                  my-kar))
+
+  ;; (import (rename (scheme base)
+  ;;                 (car my-kar)
+  ;;                 (cdr my-cdr)))
+
+  (export my-kdr my-cons))
diff --git a/tools/main.c b/tools/main.c
index 5e43f2b7..428b2764 100644
--- a/tools/main.c
+++ b/tools/main.c
@@ -2,317 +2,27 @@
  * See Copyright Notice in picrin.h
  */
 
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <getopt.h>
-
 #include "picrin.h"
-#include "picrin/pair.h"
-#include "picrin/string.h"
 #include "picrin/error.h"
 
-#if PIC_ENABLE_READLINE
-# include <editline/readline.h>
-#endif
-
-#define CODE_MAX_LENGTH 1024
-#define LINE_MAX_LENGTH 256
-
-void
-print_help(void)
-{
-  const char *help =
-    "picrin scheme\n"
-    "\n"
-    "Usage: picrin [options] [file]\n"
-    "\n"
-    "Options:\n"
-    "  -e [program]             run one liner ecript\n"
-    "  -h                       show this help";
-
-  puts(help);
-}
-
-void
-import_repllib(pic_state *pic)
-{
-  int ai = pic_gc_arena_preserve(pic);
-
-  pic_import(pic, pic_read_cstr(pic, "(scheme base)"));
-  pic_import(pic, pic_read_cstr(pic, "(scheme load)"));
-  pic_import(pic, pic_read_cstr(pic, "(scheme process-context)"));
-  pic_import(pic, pic_read_cstr(pic, "(scheme read)"));
-  pic_import(pic, pic_read_cstr(pic, "(scheme write)"));
-  pic_import(pic, pic_read_cstr(pic, "(scheme file)"));
-  pic_import(pic, pic_read_cstr(pic, "(scheme inexact)"));
-  pic_import(pic, pic_read_cstr(pic, "(scheme cxr)"));
-  pic_import(pic, pic_read_cstr(pic, "(scheme lazy)"));
-  pic_import(pic, pic_read_cstr(pic, "(scheme time)"));
-  pic_import(pic, pic_read_cstr(pic, "(picrin macro)"));
-
-#if DEBUG
-  puts("* imported repl libraries");
-#endif
-
-  pic_gc_arena_restore(pic, ai);
-}
-
-int exit_status;
-
-void
-repl(pic_state *pic)
-{
-  char code[CODE_MAX_LENGTH] = "", line[LINE_MAX_LENGTH];
-  char *prompt;
-  pic_value v, exprs;
-  int ai;
-
-#if PIC_ENABLE_READLINE
-  char *read_line;
-#else
-  char last_char;
-  int char_index;
-#endif
-
-#if PIC_ENABLE_READLINE
-  using_history();
-
-  char histfile[snprintf(NULL, 0, "%s/.picrin_history", getenv("HOME")) + 1];
-  sprintf(histfile, "%s/.picrin_history", getenv("HOME"));
-  read_history(histfile);
-#endif
-
-  ai = pic_gc_arena_preserve(pic);
-
-  while (1) {
-    prompt = code[0] == '\0' ? "> " : "* ";
-
-#if DEBUG
-    printf("[current ai = %d]\n", ai);
-#endif
-
-#if PIC_ENABLE_READLINE
-    read_line = readline(prompt);
-    if (read_line == NULL) {
-      goto eof;
-    }
-    else {
-      strncpy(line, read_line, LINE_MAX_LENGTH - 1);
-      add_history(read_line);
-      free(read_line);
-    }
-#else
-    printf("%s", prompt);
-
-    char_index = 0;
-    while ((last_char = getchar()) != '\n') {
-      if (last_char == EOF)
-	goto eof;
-      if (char_index == LINE_MAX_LENGTH)
-	goto overflow;
-      line[char_index++] = last_char;
-    }
-    line[char_index] = '\0';
-#endif
-
-    if (strlen(code) + strlen(line) >= CODE_MAX_LENGTH)
-      goto overflow;
-    strcat(code, line);
-
-    pic_try {
-
-      /* read */
-      exprs = pic_parse_cstr(pic, code);
-
-      if (pic_undef_p(exprs)) {
-        /* wait for more input */
-      }
-      else {
-        code[0] = '\0';
-
-        pic_for_each (v, exprs) {
-
-          /* eval */
-          v = pic_eval(pic, v);
-
-          /* print */
-          pic_printf(pic, "=> ~s\n", v);
-        }
-      }
-    }
-    pic_catch {
-      pic_print_backtrace(pic, pic->err);
-      pic->err = NULL;
-      code[0] = '\0';
-    }
-
-    pic_gc_arena_restore(pic, ai);
-  }
-
- eof:
-  puts("");
-  exit_status = 0;
-#if PIC_ENABLE_READLINE
-  write_history(histfile);
-#endif
-  return;
-
- overflow:
-  puts("** [fatal] line input overflow");
-  exit_status = 1;
-  return;
-}
-
-void
-exec_file(pic_state *pic, const char *fname)
-{
-  FILE *file;
-  pic_value v, exprs;
-  struct pic_proc *proc;
-
-  file = fopen(fname, "r");
-  if (file == NULL) {
-    fprintf(stderr, "fatal error: could not read %s\n", fname);
-    goto abort;
-  }
-
-  exprs = pic_parse_file(pic, file);
-  if (pic_undef_p(exprs)) {
-    fprintf(stderr, "fatal error: %s broken\n", fname);
-    goto abort;
-  }
-
-  pic_for_each (v, exprs) {
-
-    proc = pic_compile(pic, v);
-    if (proc == NULL) {
-      fputs(pic_errmsg(pic), stderr);
-      fprintf(stderr, "fatal error: %s compilation failure\n", fname);
-      goto abort;
-    }
-
-    v = pic_apply(pic, proc, pic_nil_value());
-    if (pic_undef_p(v)) {
-      fputs(pic_errmsg(pic), stderr);
-      fprintf(stderr, "fatal error: %s evaluation failure\n", fname);
-      goto abort;
-    }
-
-  }
-
-  return;
-
- abort:
-  exit_status = 1;
-  return;
-}
-
-void
-exec_string(pic_state *pic, const char *str)
-{
-  pic_value v, exprs;
-  struct pic_proc *proc;
-  int ai;
-
-  exprs = pic_parse_cstr(pic, str);
-  if (pic_undef_p(exprs)) {
-    goto abort;
-  }
-
-  ai = pic_gc_arena_preserve(pic);
-  pic_for_each (v, exprs) {
-
-    proc = pic_compile(pic, v);
-    if (proc == NULL) {
-      goto abort;
-    }
-    v = pic_apply(pic, proc, pic_nil_value());
-    if (pic_undef_p(v)) {
-      goto abort;
-    }
-
-    pic_gc_arena_restore(pic, ai);
-  }
-
-  return;
-
- abort:
-  exit_status = 1;
-  return;
-}
-
-static char *fname;
-static char *script;
-
-enum {
-  NO_MODE = 0,
-  INTERACTIVE_MODE,
-  FILE_EXEC_MODE,
-  ONE_LINER_MODE,
-} mode;
-
-void
-parse_opt(int argc, char *argv[])
-{
-  int r;
-
-  while (~(r = getopt(argc, argv, "he:"))) {
-    switch (r) {
-    case 'h':
-      print_help();
-      exit(0);
-    case 'e':
-      script = optarg;
-      mode = ONE_LINER_MODE;
-    }
-  }
-  argc -= optind;
-  argv += optind;
-
-  if (argc == 0) {
-    if (mode == NO_MODE)
-      mode = INTERACTIVE_MODE;
-  }
-  else {
-    fname = argv[0];
-    mode = FILE_EXEC_MODE;
-  }
-}
-
 int
 main(int argc, char *argv[], char **envp)
 {
   pic_state *pic;
+  int status = 0;
 
   pic = pic_open(argc, argv, envp);
 
-  parse_opt(argc, argv);
-
-  if (mode == INTERACTIVE_MODE || mode == ONE_LINER_MODE) {
-    import_repllib(pic);
+  pic_try {
+    pic_import(pic, pic_read_cstr(pic, "(picrin repl)"));
+    pic_funcall(pic, "repl", pic_nil_value());
   }
-
-  switch (mode) {
-  case NO_MODE:
-    puts("logic flaw");
-    abort();
-  case INTERACTIVE_MODE:
-    repl(pic);
-    break;
-  case FILE_EXEC_MODE:
-    exec_file(pic, fname);
-    break;
-  case ONE_LINER_MODE:
-    exec_string(pic, script);
-    break;
+  pic_catch {
+    pic_print_backtrace(pic, pic->err);
+    status = 1;
   }
 
   pic_close(pic);
 
-#if DEBUG
-  puts("* picrin successfully closed");
-#endif
-
-  return exit_status;
+  return status;
 }