Merge from S48 repository

Original commit message from Mike Sperber:


Subject: Add implementation of FOR-EACH to SRFI-1

This was missing from Olin's reference implementation.

Note that currently, the native versions of MAP and FOR-EACH already
implement the extended semantics specified by SRFI 1.  However, we
might want to enforce the R5RS restrictions to MAP and FOR-EACH at
some time in the future, so it still makes sense to have separate
implementations in SRFI 1.

scheme/srfi/srfi-1.scm

@@ -1027,6 +1027,26 @@
 ;;; We extend MAP to handle arguments of unequal length.
 (define map map-in-order)	
 
+;;; Apply F across lists, guaranteeing to go left-to-right.
+;;; NOTE: Some implementations of R5RS MAP are compliant with this spec;
+;;; in which case this procedure may simply be defined as a synonym for FOR-EACH.
+
+(define (for-each f lis1 . lists)
+  (check-arg procedure? f for-each)
+  (if (pair? lists)
+      (let recur ((lists (cons lis1 lists)))
+	(receive (cars cdrs) (%cars+cdrs lists)
+	  (if (pair? cars)
+	      (begin
+		(apply f cars)		; Do head first,
+		(recur cdrs)))))	; then tail.
+	    
+      ;; Fast path.
+      (let recur ((lis lis1))
+	(if (not (null-list? lis))
+	    (begin
+	      (f (car lis))		; Do head first,
+	      (recur (cdr lis)))))))	; then tail.
 
 ;;; filter, remove, partition
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;