From: Chris Hanson <org/chris-hanson/cph>
Date: Mon, 12 Jun 2006 17:53:14 +0000 (+0000)
Subject: Finish integrating SRFI-1 support.
X-Git-Tag: 20090517-FFI~1011
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=14e7423b76e40b4a6cf6c98f945f789a557b43e2;p=mit-scheme.git

Finish integrating SRFI-1 support.
---

diff --git a/v7/src/runtime/advice.scm b/v7/src/runtime/advice.scm
index 96d3621b3..911017f5c 100644
--- a/v7/src/runtime/advice.scm
+++ b/v7/src/runtime/advice.scm
@@ -1,9 +1,9 @@
 #| -*-Scheme-*-
 
-$Id: advice.scm,v 14.20 2003/02/14 18:28:32 cph Exp $
+$Id: advice.scm,v 14.21 2006/06/12 17:53:02 cph Exp $
 
 Copyright 1986,1987,1988,1989,1990,1993 Massachusetts Institute of Technology
-Copyright 1999,2000,2003 Massachusetts Institute of Technology
+Copyright 1999,2000,2003,2006 Massachusetts Institute of Technology
 
 This file is part of MIT/GNU Scheme.
 
@@ -338,8 +338,6 @@ USA.
 (define (break-both procedure)
   (advise-both procedure break-entry-advice break-exit-advice))
 
-(define break break-both)
-
 (define unbreak-entry
   (specific-entry-unadviser break-entry-advice))
 
diff --git a/v7/src/runtime/list.scm b/v7/src/runtime/list.scm
index c4974b6cb..076ff5ae2 100644
--- a/v7/src/runtime/list.scm
+++ b/v7/src/runtime/list.scm
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: list.scm,v 14.51 2006/06/12 05:07:09 cph Exp $
+$Id: list.scm,v 14.52 2006/06/12 17:53:05 cph Exp $
 
 Copyright 1986,1987,1988,1989,1990,1991 Massachusetts Institute of Technology
 Copyright 1992,1993,1994,1995,1996,2000 Massachusetts Institute of Technology
@@ -318,6 +318,9 @@ USA.
     (if (pair? tree)
 	(cons (walk (car tree)) (walk (cdr tree)))
 	tree)))
+
+(define (car+cdr pair)
+  (values (car pair) (cdr pair)))
 
 ;;;; Weak Pairs
 
@@ -406,7 +409,7 @@ USA.
 			items*))
 		  (begin
 		    (if (not (null? items*))
-			(error:not-weak-list items 'WEAK-MEMQ))
+			(error:not-weak-list items 'WEAK-DELQ!))
 		    '()))))
 	   (locate-initial-segment
 	    (lambda (last this)
@@ -417,7 +420,7 @@ USA.
 				(trim-initial-segment (system-pair-cdr this)))
 		      (locate-initial-segment this (system-pair-cdr this)))
 		  (if (not (null? this))
-		      (error:not-weak-list items 'WEAK-MEMQ))))))
+		      (error:not-weak-list items 'WEAK-DELQ!))))))
     (trim-initial-segment items)))
 
 ;;;; Standard Selectors
@@ -946,138 +949,108 @@ USA.
 ;;;; Membership lists
 
 (define (memq item items)
-  (let loop ((items* items))
-    (if (pair? items*)
-	(if (eq? (car items*) item)
-	    items*
-	    (loop (cdr items*)))
-	(begin
-	  (if (not (null? items*))
-	      (error:not-list items 'MEMQ))
-	  #f))))
+  (%member item items eq? 'MEMQ))
 
 (define (memv item items)
-  (let loop ((items* items))
-    (if (pair? items*)
-	(if (eqv? (car items*) item)
-	    items*
-	    (loop (cdr items*)))
-	(begin
-	  (if (not (null? items*))
-	      (error:not-list items 'MEMV))
-	  #f))))
+  (%member item items eqv? 'MEMV))
 
-(define (member item items #!optional predicate)
-  (let ((predicate (if (default-object? predicate) equal? predicate)))
-    (let loop ((items* items))
-      (if (pair? items*)
-	  (if (predicate (car items*) item)
-	      items*
-	      (loop (cdr items*)))
-	  (begin
-	    (if (not (null? items*))
-		(error:not-list items 'MEMBER))
-	    #f)))))
+(define (member item items #!optional =)
+  (let ((= (if (default-object? =) equal? =)))
+    (%member item items = 'MEMBER)))
 
-(define (member-procedure predicate #!optional caller)
+(define (member-procedure = #!optional caller)
   (lambda (item items)
-    (let loop ((items* items))
-      (if (pair? items*)
-	  (if (predicate (car items*) item)
-	      items*
-	      (loop (cdr items*)))
+    (%member item items = caller)))
+
+(define (add-member-procedure = #!optional caller)
+  (lambda (item items)
+    (if (%member item items = caller)
+	items
+	(cons item items))))
+
+(define-integrable (%member item items = caller)
+  (let ((lose (lambda () (error:not-list items caller))))
+    (let loop ((items items))
+      (if (pair? items)
+	  (if (= (car items) item)
+	      items
+	      (loop (cdr items)))
 	  (begin
-	    (if (not (null? items*))
-		(error:not-list items caller))
+	    (if (not (null? items))
+		(lose))
 	    #f)))))
-
-(define delq)
-(define delv)
-(define delete)
-
-(let-syntax
-    ((fast-delete-member
-      (sc-macro-transformer
-       (lambda (form environment)
-	 (if (syntax-match? '(SYMBOL IDENTIFIER) (cdr form))
-	     (let ((name (cadr form))
-		   (predicate (close-syntax (caddr form) environment)))
-	       `(SET!
-		 ,name
-		 (NAMED-LAMBDA (,name ITEM ITEMS)
-		   (LET ((LOSE (LAMBDA () (ERROR:NOT-LIST ITEMS ',name))))
-		     (COND ((PAIR? ITEMS)
-			    (LET ((HEAD (CONS (CAR ITEMS) '())))
-			      (LET LOOP ((ITEMS (CDR ITEMS)) (PREVIOUS HEAD))
-				(COND ((PAIR? ITEMS)
-				       (IF (,predicate (CAR ITEMS) ITEM)
-					   (LOOP (CDR ITEMS) PREVIOUS)
-					   (LET ((NEW (CONS (CAR ITEMS) '())))
-					     (SET-CDR! PREVIOUS NEW)
-					     (LOOP (CDR ITEMS) NEW))))
-				      ((NOT (NULL? ITEMS)) (LOSE))))
-			      (IF (,predicate (CAR ITEMS) ITEM)
-				  (CDR HEAD)
-				  HEAD)))
-			   ((NULL? ITEMS) ITEMS)
-			   (ELSE (LOSE)))))))
-	     (ill-formed-syntax form))))))
-  (fast-delete-member delq eq?)
-  (fast-delete-member delv eqv?)
-  (fast-delete-member delete equal?))
-
-(define (add-member-procedure predicate #!optional caller)
-  (let ((member (member-procedure predicate caller)))
-    (lambda (item items)
-      (if (member item items)
-	  items
-	  (cons item items)))))
 
 (define ((delete-member-procedure deletor predicate) item items)
   ((deletor (lambda (match) (predicate match item))) items))
 
-(define delq!)
-(define delv!)
-(define delete!)
+(define (delq item items)
+  (%delete item items eq? 'DELQ))
+
+(define (delv item items)
+  (%delete item items eqv? 'DELQ))
+
+(define (delete item items #!optional =)
+  (let ((= (if (default-object? =) equal? =)))
+    (%delete item items = 'DELETE)))
+
+(define-integrable (%delete item items = caller)
+  (let ((lose (lambda () (error:not-list items caller))))
+    (if (pair? items)
+	(let ((head (cons (car items) '())))
+	  (let loop ((items (cdr items)) (previous head))
+	    (cond ((pair? items)
+		   (if (= (car items) item)
+		       (loop (cdr items) previous)
+		       (let ((new (cons (car items) '())))
+			 (set-cdr! previous new)
+			 (loop (cdr items) new))))
+		  ((not (null? items))
+		   (lose))))
+	  (if (= (car items) item)
+	      (cdr head)
+	      head))
+	(begin
+	  (if (not (null? items))
+	      (lose))
+	  items))))
 
-(let-syntax
-    ((fast-delete-member!
-      (sc-macro-transformer
-       (lambda (form environment)
-	 (if (syntax-match? '(SYMBOL IDENTIFIER) (cdr form))
-	     (let ((name (cadr form))
-		   (predicate (close-syntax (caddr form) environment)))
-	       `(SET!
-		 ,name
-		 (NAMED-LAMBDA (,name ITEM ITEMS)
-		   (LETREC
-		       ((TRIM-INITIAL-SEGMENT
-			 (LAMBDA (ITEMS*)
-			   (IF (PAIR? ITEMS*)
-			       (IF (,predicate ITEM (CAR ITEMS*))
-				   (TRIM-INITIAL-SEGMENT (CDR ITEMS*))
-				   (BEGIN
-				     (LOCATE-INITIAL-SEGMENT ITEMS*
-							     (CDR ITEMS*))
-				     ITEMS*))
-			       (BEGIN
-				 (IF (NOT (NULL? ITEMS*))
-				     (ERROR:NOT-LIST ITEMS ',name))
-				 '()))))
-			(LOCATE-INITIAL-SEGMENT
-			 (LAMBDA (LAST THIS)
-			   (IF (PAIR? THIS)
-			       (IF (,predicate ITEM (CAR THIS))
-				   (SET-CDR! LAST
-					     (TRIM-INITIAL-SEGMENT (CDR THIS)))
-				   (LOCATE-INITIAL-SEGMENT THIS (CDR THIS)))
-			       (IF (NOT (NULL? THIS))
-				   (ERROR:NOT-LIST ITEMS ',name))))))
-		     (TRIM-INITIAL-SEGMENT ITEMS)))))
-	     (ill-formed-syntax form))))))
-  (fast-delete-member! delq! eq?)
-  (fast-delete-member! delv! eqv?)
-  (fast-delete-member! delete! equal?))
+(define (delq! item items)
+  (%delete! item items eq? 'DELQ!))
+
+(define (delv! item items)
+  (%delete! item items eqv? 'DELV!))
+
+(define (delete! item items #!optional =)
+  (let ((= (if (default-object? =) equal? =)))
+    (%delete! item items = 'DELETE!)))
+
+(define-integrable (%delete! item items = caller)
+  (letrec
+      ((trim-initial-segment
+	(lambda (items)
+	  (if (pair? items)
+	      (if (= item (car items))
+		  (trim-initial-segment (cdr items))
+		  (begin
+		    (locate-initial-segment items (cdr items))
+		    items))
+	      (begin
+		(if (not (null? items))
+		    (lose))
+		'()))))
+       (locate-initial-segment
+	(lambda (last this)
+	  (if (pair? this)
+	      (if (= item (car this))
+		  (set-cdr! last
+			    (trim-initial-segment (cdr this)))
+		  (locate-initial-segment this (cdr this)))
+	      (if (not (null? this))
+		  (error:not-list items caller)))))
+       (lose
+	(lambda ()
+	  (error:not-list items caller))))
+    (trim-initial-segment items)))
 
 ;;;; Association lists
 
@@ -1086,149 +1059,8 @@ USA.
 
 (define-guarantee alist "association list")
 
-(define (assq key alist)
-  (let loop ((alist* alist))
-    (if (pair? alist*)
-	(begin
-	  (if (not (pair? (car alist*)))
-	      (error:not-alist alist 'ASSQ))
-	  (if (eq? (caar alist*) key)
-	      (car alist*)
-	      (loop (cdr alist*))))
-	(begin
-	  (if (not (null? alist*))
-	      (error:not-alist alist 'ASSQ))
-	  #f))))
-
-(define (assv key alist)
-  (let loop ((alist* alist))
-    (if (pair? alist*)
-	(begin
-	  (if (not (pair? (car alist*)))
-	      (error:not-alist alist 'ASSV))
-	  (if (eqv? (caar alist*) key)
-	      (car alist*)
-	      (loop (cdr alist*))))
-	(begin
-	  (if (not (null? alist*))
-	      (error:not-alist alist 'ASSV))
-	  #f))))
-
-(define (assoc key alist #!optional predicate)
-  (let ((predicate (if (default-object? predicate) equal? predicate)))
-    (let loop ((alist* alist))
-      (if (pair? alist*)
-	  (begin
-	    (if (not (pair? (car alist*)))
-		(error:not-alist alist 'ASSOC))
-	    (if (predicate (caar alist*) key)
-		(car alist*)
-		(loop (cdr alist*))))
-	  (begin
-	    (if (not (null? alist*))
-		(error:not-alist alist 'ASSOC))
-	    #f)))))
-
-(define (association-procedure predicate selector #!optional caller)
-  (lambda (key items)
-    (let loop ((items* items))
-      (if (pair? items*)
-	  (if (predicate (selector (car items*)) key)
-	      (car items*)
-	      (loop (cdr items*)))
-	  (begin
-	    (if (not (null? items*))
-		(error:not-list items caller))
-	    #f)))))
-
-(define del-assq)
-(define del-assv)
-(define del-assoc)
-
-(let-syntax
-    ((fast-del-assoc
-      (sc-macro-transformer
-       (lambda (form environment)
-	 (if (syntax-match? '(SYMBOL IDENTIFIER) (cdr form))
-	     (let ((name (cadr form))
-		   (predicate (close-syntax (caddr form) environment)))
-	       `(SET!
-		 ,name
-		 (NAMED-LAMBDA (,name ITEM ITEMS)
-		   (LET ((LOSE (LAMBDA () (ERROR:NOT-ALIST ITEMS ',name))))
-		     (COND ((PAIR? ITEMS)
-			    (IF (NOT (PAIR? (CAR ITEMS))) (LOSE))
-			    (LET ((HEAD (CONS (CAR ITEMS) '())))
-			      (LET LOOP ((ITEMS* (CDR ITEMS)) (PREVIOUS HEAD))
-				(COND ((PAIR? ITEMS*)
-				       (IF (NOT (PAIR? (CAR ITEMS*))) (LOSE))
-				       (IF (,predicate (CAAR ITEMS*) ITEM)
-					   (LOOP (CDR ITEMS*) PREVIOUS)
-					   (LET ((NEW (CONS (CAR ITEMS*) '())))
-					     (SET-CDR! PREVIOUS NEW)
-					     (LOOP (CDR ITEMS*) NEW))))
-				      ((NOT (NULL? ITEMS*)) (LOSE))))
-			      (IF (,predicate (CAAR ITEMS) ITEM)
-				  (CDR HEAD)
-				  HEAD)))
-			   ((NULL? ITEMS) ITEMS)
-			   (ELSE (LOSE)))))))
-	     (ill-formed-syntax form))))))
-  (fast-del-assoc del-assq eq?)
-  (fast-del-assoc del-assv eqv?)
-  (fast-del-assoc del-assoc equal?))
-
-(define ((delete-association-procedure deletor predicate selector) key alist)
-  ((deletor (lambda (entry) (predicate (selector entry) key))) alist))
-
-(define del-assq!)
-(define del-assv!)
-(define del-assoc!)
-
-(let-syntax
-    ((fast-del-assoc!
-      (sc-macro-transformer
-       (lambda (form environment)
-	 (if (syntax-match? '(SYMBOL IDENTIFIER) (cdr form))
-	     (let ((name (cadr form))
-		   (predicate (close-syntax (caddr form) environment)))
-	       `(SET!
-		 ,name
-		 (NAMED-LAMBDA (,name ITEM ITEMS)
-		   (LETREC
-		       ((TRIM-INITIAL-SEGMENT
-			 (LAMBDA (ITEMS*)
-			   (IF (PAIR? ITEMS*)
-			       (BEGIN
-				 (IF (NOT (PAIR? (CAR ITEMS*))) (LOSE))
-				 (IF (,predicate (CAAR ITEMS*) ITEM)
-				     (TRIM-INITIAL-SEGMENT (CDR ITEMS*))
-				     (BEGIN
-				       (LOCATE-INITIAL-SEGMENT ITEMS*
-							       (CDR ITEMS*))
-				       ITEMS*)))
-			       (BEGIN
-				 (IF (NOT (NULL? ITEMS*)) (LOSE))
-				 '()))))
-			(LOCATE-INITIAL-SEGMENT
-			 (LAMBDA (LAST THIS)
-			   (COND ((PAIR? THIS)
-				  (IF (NOT (PAIR? (CAR THIS))) (LOSE))
-				  (IF (,predicate (CAAR THIS) ITEM)
-				      (SET-CDR!
-				       LAST
-				       (TRIM-INITIAL-SEGMENT (CDR THIS)))
-				      (LOCATE-INITIAL-SEGMENT THIS
-							      (CDR THIS))))
-				 ((NOT (NULL? THIS)) (LOSE)))))
-			(LOSE
-			 (LAMBDA ()
-			   (ERROR:NOT-ALIST ITEMS ',name))))
-		     (TRIM-INITIAL-SEGMENT ITEMS)))))
-	     (ill-formed-syntax form))))))
-  (fast-del-assoc! del-assq! eq?)
-  (fast-del-assoc! del-assv! eqv?)
-  (fast-del-assoc! del-assoc! equal?))
+(define (alist-cons key datum alist)
+  (cons (cons key datum) alist))
 
 (define (alist-copy alist)
   (let ((lose (lambda () (error:not-alist alist 'ALIST-COPY))))
@@ -1249,6 +1081,133 @@ USA.
 	       (lose)))
 	  ((null? alist) alist)
 	  (else (lose)))))
+
+(define (association-procedure predicate selector #!optional caller)
+  (lambda (key items)
+    (let ((lose (lambda () (error:not-list items caller))))
+      (let loop ((items items))
+	(if (pair? items)
+	    (if (predicate (selector (car items)) key)
+		(car items)
+		(loop (cdr items)))
+	    (begin
+	      (if (not (null? items))
+		  (lose))
+	      #f))))))
+
+(define ((delete-association-procedure deletor predicate selector) key alist)
+  ((deletor (lambda (entry) (predicate (selector entry) key))) alist))
+
+(define (assq key alist)
+  (%assoc key alist eq? 'ASSQ))
+
+(define (assv key alist)
+  (%assoc key alist eqv? 'ASSV))
+
+(define (assoc key alist #!optional =)
+  (let ((= (if (default-object? =) equal? =)))
+    (%assoc key alist = 'ASSOC)))
+
+(define-integrable (%assoc key alist = caller)
+  (let ((lose (lambda () (error:not-alist alist caller))))
+    (let loop ((alist alist))
+      (if (pair? alist)
+	  (begin
+	    (if (not (pair? (car alist)))
+		(lose))
+	    (if (= (caar alist) key)
+		(car alist)
+		(loop (cdr alist))))
+	  (begin
+	    (if (not (null? alist))
+		(lose))
+	    #f)))))
+
+(define (del-assq key alist)
+  (%alist-delete key alist eq? 'DEL-ASSQ))
+
+(define (del-assv key alist)
+  (%alist-delete key alist eqv? 'DEL-ASSV))
+
+(define (del-assoc key alist)
+  (%alist-delete key alist equal? 'DEL-ASSOC))
+
+(define (alist-delete key alist #!optional =)
+  (let ((= (if (default-object? =) equal? =)))
+    (%alist-delete key alist = 'ALIST-DELETE)))
+
+(define-integrable (%alist-delete key alist = caller)
+  (let ((lose (lambda () (error:not-alist alist caller))))
+    (if (pair? alist)
+	(begin
+	  (if (not (pair? (car alist)))
+	      (lose))
+	  (let ((head (cons (car alist) '())))
+	    (let loop ((alist (cdr alist)) (previous head))
+	      (cond ((pair? alist)
+		     (if (not (pair? (car alist)))
+			 (lose))
+		     (if (= (caar alist) key)
+			 (loop (cdr alist) previous)
+			 (let ((new (cons (car alist) '())))
+			   (set-cdr! previous new)
+			   (loop (cdr alist) new))))
+		    ((not (null? alist))
+		     (lose))))
+	    (if (= (caar alist) key)
+		(cdr head)
+		head)))
+	(begin
+	  (if (not (null? alist))
+	      (lose))
+	  alist))))
+
+(define (del-assq! key alist)
+  (%alist-delete! key alist eq? 'DEL-ASSQ!))
+
+(define (del-assv! key alist)
+  (%alist-delete! key alist eqv? 'DEL-ASSV!))
+
+(define (del-assoc! key alist)
+  (%alist-delete! key alist equal? 'DEL-ASSOC!))
+
+(define (alist-delete! key alist #!optional =)
+  (let ((= (if (default-object? =) equal? =)))
+    (%alist-delete! key alist = 'ALIST-DELETE!)))
+
+(define-integrable (%alist-delete! item items = caller)
+  (letrec
+      ((trim-initial-segment
+	(lambda (items)
+	  (if (pair? items)
+	      (begin
+		(if (not (pair? (car items)))
+		    (lose))
+		(if (= (caar items) item)
+		    (trim-initial-segment (cdr items))
+		    (begin
+		      (locate-initial-segment items (cdr items))
+		      items)))
+	      (begin
+		(if (not (null? items))
+		    (lose))
+		'()))))
+       (locate-initial-segment
+	(lambda (last this)
+	  (cond ((pair? this)
+		 (if (not (pair? (car this)))
+		     (lose))
+		 (if (= (caar this) item)
+		     (set-cdr!
+		      last
+		      (trim-initial-segment (cdr this)))
+		     (locate-initial-segment this (cdr this))))
+		((not (null? this))
+		 (lose)))))
+       (lose
+	(lambda ()
+	  (error:not-alist items caller))))
+    (trim-initial-segment items)))
 
 ;;;; Keyword lists
 
@@ -1340,11 +1299,11 @@ USA.
   (if (not (pair? (cdr list)))
       '()
       (let ((head (cons (car list) '())))
-	(let loop ((list* (cdr list)) (previous head))
-	  (if (pair? (cdr list*))
-	      (let ((new (cons (car list*) '())))
+	(let loop ((list (cdr list)) (previous head))
+	  (if (pair? (cdr list))
+	      (let ((new (cons (car list) '())))
 		(set-cdr! previous new)
-		(loop (cdr list*) new))
+		(loop (cdr list) new))
 	      head)))))
 
 (define (except-last-pair! list)
diff --git a/v7/src/runtime/mit-syntax.scm b/v7/src/runtime/mit-syntax.scm
index 159384039..4274c546c 100644
--- a/v7/src/runtime/mit-syntax.scm
+++ b/v7/src/runtime/mit-syntax.scm
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: mit-syntax.scm,v 14.25 2006/02/26 03:00:43 cph Exp $
+$Id: mit-syntax.scm,v 14.26 2006/06/12 17:53:08 cph Exp $
 
 Copyright 1989,1990,1991,2001,2002,2003 Massachusetts Institute of Technology
 Copyright 2004,2005,2006 Massachusetts Institute of Technology
@@ -335,6 +335,7 @@ USA.
 
 (define supported-srfi-features
   '(SRFI-0
+    SRFI-1
     SRFI-2
     SRFI-6
     SRFI-8
diff --git a/v7/src/runtime/runtime.pkg b/v7/src/runtime/runtime.pkg
index 1a8839f98..8bfc0a18d 100644
--- a/v7/src/runtime/runtime.pkg
+++ b/v7/src/runtime/runtime.pkg
@@ -1,6 +1,6 @@
 #| -*-Scheme-*-
 
-$Id: runtime.pkg,v 14.584 2006/06/12 05:07:18 cph Exp $
+$Id: runtime.pkg,v 14.585 2006/06/12 17:53:11 cph Exp $
 
 Copyright 1988,1989,1990,1991,1992,1993 Massachusetts Institute of Technology
 Copyright 1994,1995,1996,1997,1998,1999 Massachusetts Institute of Technology
@@ -932,7 +932,7 @@ USA.
 	  advice
 	  advise-entry
 	  advise-exit
-	  break
+	  ;;break
 	  break-both
 	  break-entry
 	  break-exit
@@ -2126,7 +2126,10 @@ USA.
 	  (proper-list? list?)		;SRFI-1
 	  add-member-procedure
 	  alist->keyword-list
+	  alist-cons
 	  alist-copy
+	  alist-delete
+	  alist-delete!
 	  alist?
 	  append
 	  append!
@@ -2153,6 +2156,7 @@ USA.
 	  caddr
 	  cadr
 	  car
+	  car+cdr			;SRFI-1
 	  cdaaar
 	  cdaadr
 	  cdaar
@@ -2293,6 +2297,72 @@ USA.
 	  weak-set-cdr!
 	  xcons))
 
+(define-package (runtime srfi-1)
+  (files "srfi-1")
+  (parent (runtime))
+  (export ()
+	  any
+	  append-reverse
+	  append-reverse!
+	  break
+	  break!
+	  concatenate
+	  concatenate!
+	  count
+	  delete-duplicates
+	  delete-duplicates!
+	  drop
+	  drop-right
+	  drop-right!
+	  drop-while
+	  every
+	  filter
+	  filter!
+	  filter-map
+	  find
+	  find-tail
+	  length+
+	  list-index
+	  lset-adjoin
+	  lset-diff+intersection
+	  lset-diff+intersection!
+	  lset-difference
+	  lset-difference!
+	  lset-intersection
+	  lset-intersection!
+	  lset-union
+	  lset-union!
+	  lset-xor
+	  lset-xor!
+	  lset<=
+	  lset=
+	  map!
+	  map-in-order
+	  pair-fold
+	  pair-fold-right
+	  pair-for-each
+	  partition
+	  partition!
+	  remove
+	  remove!
+	  span
+	  span!
+	  split-at
+	  split-at!
+	  take
+	  take!
+	  take-right
+	  take-while
+	  take-while!
+	  unfold
+	  unfold-right
+	  unzip1
+	  unzip2
+	  unzip3
+	  unzip4
+	  unzip5
+	  zip))
+
 (define-package (runtime load)
   (files "load")
   (parent (runtime))
diff --git a/v7/src/runtime/srfi-1.scm b/v7/src/runtime/srfi-1.scm
new file mode 100644
index 000000000..6979f8abd
--- /dev/null
+++ b/v7/src/runtime/srfi-1.scm
@@ -0,0 +1,1049 @@
+#| -*- Scheme -*-
+
+Copyright (c) 1998, 1999 by Olin Shivers. You may do as you please with
+this code as long as you do not remove this copyright notice or
+hold me liable for its use. Please send bug reports to shivers at
+ai.mit.edu.
+    -Olin
+
+This implementation heavily modified by John Kraemer and Chris
+Hanson for inclusion in MIT/GNU Scheme.
+
+$Id: srfi-1.scm,v 1.1 2006/06/12 17:53:14 cph Exp $
+
+Copyright 2006 Massachusetts Institute of Technology
+
+This file is part of MIT/GNU Scheme.
+
+MIT/GNU Scheme is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or (at
+your option) any later version.
+
+MIT/GNU Scheme is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with MIT/GNU Scheme; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+USA.
+
+|#
+
+;;;; SRFI-1 list-processing library
+
+(declare (usual-integrations))
+
+;;; [Olin's original notes]
+
+;;; This is a library of list- and pair-processing functions. I wrote it after
+;;; carefully considering the functions provided by the libraries found in
+;;; R4RS/R5RS Scheme, MIT Scheme, Gambit, RScheme, MzScheme, slib, Common
+;;; Lisp, Bigloo, guile, T, APL and the SML standard basis. It is a pretty
+;;; rich toolkit, providing a superset of the functionality found in any of
+;;; the various Schemes I considered.
+
+;;; This implementation is intended as a portable reference implementation
+;;; for SRFI-1. See the porting notes below for more information.
+
+;;; Exported:
+;;; xcons tree-copy make-list list-tabulate cons* list-copy
+;;; proper-list? circular-list? dotted-list? not-pair? null-list? list=
+;;; circular-list length+
+;;; iota
+;;; first second third fourth fifth sixth seventh eighth ninth tenth
+;;; car+cdr
+;;; take       drop
+;;; take-right drop-right
+;;; take!      drop-right!
+;;; split-at   split-at!
+;;; last last-pair
+;;; zip unzip1 unzip2 unzip3 unzip4 unzip5
+;;; count
+;;; append! append-reverse append-reverse! concatenate concatenate!
+;;; unfold       fold       pair-fold       reduce
+;;; unfold-right fold-right pair-fold-right reduce-right
+;;; append-map append-map! map! pair-for-each filter-map map-in-order
+;;; filter  partition  remove
+;;; filter! partition! remove!
+;;; find find-tail any every list-index
+;;; take-while drop-while take-while!
+;;; span break span! break!
+;;; delete delete!
+;;; alist-cons alist-copy
+;;; delete-duplicates delete-duplicates!
+;;; alist-delete alist-delete!
+;;; reverse!
+;;; lset<= lset= lset-adjoin
+;;; lset-union  lset-intersection  lset-difference  lset-xor
+;;; lset-union! lset-intersection! lset-difference! lset-xor!
+;;; lset-diff+intersection
+;;; lset-diff+intersection!
+
+;;; In principle, the following R4RS list- and pair-processing procedures
+;;; are also part of this package's exports, although they are not defined
+;;; in this file:
+;;;   Primitives: cons pair? null? car cdr set-car! set-cdr!
+;;;   Non-primitives: list length append reverse cadr ... cddddr list-ref
+;;;                   memq memv assq assv
+;;;   (The non-primitives are defined in this file, but commented out.)
+
+;;; These R4RS procedures have extended definitions in SRFI-1 and are defined
+;;; in this file:
+;;;   map for-each member assoc
+
+;;; The remaining two R4RS list-processing procedures are not included:
+;;;   list-tail (use drop)
+;;;   list? (use proper-list?)
+
+;;; A note on recursion and iteration/reversal:
+;;; Many iterative list-processing algorithms naturally compute the elements
+;;; of the answer list in the wrong order (left-to-right or head-to-tail) from
+;;; the order needed to cons them into the proper answer (right-to-left, or
+;;; tail-then-head). One style or idiom of programming these algorithms, then,
+;;; loops, consing up the elements in reverse order, then destructively
+;;; reverses the list at the end of the loop. I do not do this. The natural
+;;; and efficient way to code these algorithms is recursively. This trades off
+;;; intermediate temporary list structure for intermediate temporary stack
+;;; structure. In a stack-based system, this improves cache locality and
+;;; lightens the load on the GC system. Don't stand on your head to iterate!
+;;; Recurse, where natural. Multiple-value returns make this even more
+;;; convenient, when the recursion/iteration has multiple state values.
+
+;;; Porting:
+;;; This is carefully tuned code; do not modify casually.
+;;;   - It is careful to share storage when possible;
+;;;   - Side-effecting code tries not to perform redundant writes.
+
+;;; That said, a port of this library to a specific Scheme system might wish
+;;; to tune this code to exploit particulars of the implementation.
+;;; The single most important compiler-specific optimisation you could make
+;;; to this library would be to add rewrite rules or transforms to:
+;;; - transform applications of n-ary procedures (e.g. LIST=, CONS*, APPEND,
+;;;   LSET-UNION) into multiple applications of a primitive two-argument
+;;;   variant.
+;;; - transform applications of the mapping functions (MAP, FOR-EACH, FOLD,
+;;;   ANY, EVERY) into open-coded loops. The killer here is that these
+;;;   functions are n-ary. Handling the general case is quite inefficient,
+;;;   requiring many intermediate data structures to be allocated and
+;;;   discarded.
+;;; - transform applications of procedures that take optional arguments
+;;;   into calls to variants that do not take optional arguments. This
+;;;   eliminates unnecessary consing and parsing of the rest parameter.
+
+;;; These transforms would provide BIG speedups. In particular, the n-ary
+;;; mapping functions are particularly slow and cons-intensive, and are good
+;;; candidates for tuning. I have coded fast paths for the single-list cases,
+;;; but what you really want to do is exploit the fact that the compiler
+;;; usually knows how many arguments are being passed to a particular
+;;; application of these functions -- they are usually explicitly called, not
+;;; passed around as higher-order values. If you can arrange to have your
+;;; compiler produce custom code or custom linkages based on the number of
+;;; arguments in the call, you can speed these functions up a *lot*. But this
+;;; kind of compiler technology no longer exists in the Scheme world as far as
+;;; I can see.
+
+;;; Note that this code is, of course, dependent upon standard bindings for
+;;; the R5RS procedures -- i.e., it assumes that the variable CAR is bound
+;;; to the procedure that takes the car of a list. If your Scheme
+;;; implementation allows user code to alter the bindings of these procedures
+;;; in a manner that would be visible to these definitions, then there might
+;;; be trouble. You could consider horrible kludgery along the lines of
+;;;    (define fact
+;;;      (let ((= =) (- -) (* *))
+;;;        (letrec ((real-fact (lambda (n)
+;;;                              (if (= n 0) 1 (* n (real-fact (- n 1)))))))
+;;;          real-fact)))
+;;; Or you could consider shifting to a reasonable Scheme system that, say,
+;;; has a module system protecting code from this kind of lossage.
+
+;;; This code does a fair amount of run-time argument checking. If your
+;;; Scheme system has a sophisticated compiler that can eliminate redundant
+;;; error checks, this is no problem. However, if not, these checks incur
+;;; some performance overhead -- and, in a safe Scheme implementation, they
+;;; are in some sense redundant: if we don't check to see that the PROC
+;;; parameter is a procedure, we'll find out anyway three lines later when
+;;; we try to call the value. It's pretty easy to rip all this argument
+;;; checking code out if it's inappropriate for your implementation -- just
+;;; nuke every call to CHECK-ARG.
+
+;;; On the other hand, if you *do* have a sophisticated compiler that will
+;;; actually perform soft-typing and eliminate redundant checks (Rice's systems
+;;; being the only possible candidate of which I'm aware), leaving these checks
+;;; in can *help*, since their presence can be elided in redundant cases,
+;;; and in cases where they are needed, performing the checks early, at
+;;; procedure entry, can "lift" a check out of a loop.
+
+;;; Finally, I have only checked the properties that can portably be checked
+;;; with R5RS Scheme -- and this is not complete. You may wish to alter
+;;; the CHECK-ARG parameter checks to perform extra, implementation-specific
+;;; checks, such as procedure arity for higher-order values.
+
+;;; The code has only these non-R4RS dependencies:
+;;;   A few calls to an ERROR procedure;
+;;;   Uses of the R5RS multiple-value procedure VALUES and the m-v binding
+;;;     RECEIVE macro (which isn't R5RS, but is a trivial macro).
+;;;   Many calls to a parameter-checking procedure check-arg:
+;;;    (define (check-arg pred val caller)
+;;;      (let lp ((val val))
+;;;        (if (pred val) val (lp (error "Bad argument" val pred caller)))))
+;;;   A few uses of the LET-OPTIONAL and :OPTIONAL macros for parsing
+;;;     optional arguments.
+
+;;; Most of these procedures use the NULL-LIST? test to trigger the
+;;; base case in the inner loop or recursion. The NULL-LIST? function
+;;; is defined to be a careful one -- it raises an error if passed a
+;;; non-nil, non-pair value. The spec allows an implementation to use
+;;; a less-careful implementation that simply defines NULL-LIST? to
+;;; be NOT-PAIR?. This would speed up the inner loops of these procedures
+;;; at the expense of having them silently accept dotted lists.
+
+;;; A note on dotted lists:
+;;; I, personally, take the view that the only consistent view of lists
+;;; in Scheme is the view that *everything* is a list -- values such as
+;;; 3 or "foo" or 'bar are simply empty dotted lists. This is due to the
+;;; fact that Scheme actually has no true list type. It has a pair type,
+;;; and there is an *interpretation* of the trees built using this type
+;;; as lists.
+;;;
+;;; I lobbied to have these list-processing procedures hew to this
+;;; view, and accept any value as a list argument. I was overwhelmingly
+;;; overruled during the SRFI discussion phase. So I am inserting this
+;;; text in the reference lib and the SRFI spec as a sort of "minority
+;;; opinion" dissent.
+;;;
+;;; Many of the procedures in this library can be trivially redefined
+;;; to handle dotted lists, just by changing the NULL-LIST? base-case
+;;; check to NOT-PAIR?, meaning that any non-pair value is taken to be
+;;; an empty list. For most of these procedures, that's all that is
+;;; required.
+;;;
+;;; However, we have to do a little more work for some procedures that
+;;; *produce* lists from other lists.  Were we to extend these procedures to
+;;; accept dotted lists, we would have to define how they terminate the lists
+;;; produced as results when passed a dotted list. I designed a coherent set
+;;; of termination rules for these cases; this was posted to the SRFI-1
+;;; discussion list. I additionally wrote an earlier version of this library
+;;; that implemented that spec. It has been discarded during later phases of
+;;; the definition and implementation of this library.
+;;;
+;;; The argument *against* defining these procedures to work on dotted
+;;; lists is that dotted lists are the rare, odd case, and that by
+;;; arranging for the procedures to handle them, we lose error checking
+;;; in the cases where a dotted list is passed by accident -- e.g., when
+;;; the programmer swaps a two arguments to a list-processing function,
+;;; one being a scalar and one being a list. For example,
+;;;     (member '(1 3 5 7 9) 7)
+;;; This would quietly return #f if we extended MEMBER to accept dotted
+;;; lists.
+;;;
+;;; The SRFI discussion record contains more discussion on this topic.
+
+;;;; Selectors
+
+(define (take lis k)
+  (guarantee-index-fixnum k 'TAKE)
+  (let recur ((lis lis) (k k))
+    (if (fix:> k 0)
+	(cons (car lis)
+	      (recur (cdr lis) (fix:- k 1)))
+	'())))
+
+(define (drop lis k)
+  (guarantee-index-fixnum k 'DROP)
+  (%drop lis k))
+
+(define (%drop lis k)
+  (let iter ((lis lis) (k k))
+    (if (fix:> k 0)
+	(iter (cdr lis) (fix:- k 1))
+	lis)))
+
+(define (take! lis k)
+  (guarantee-index-fixnum k 'TAKE!)
+  (if (fix:> k 0)
+      (begin
+	(set-cdr! (drop lis (fix:- k 1)) '())
+	lis)
+      '()))
+
+;;; TAKE-RIGHT and DROP-RIGHT work by getting two pointers into the list,
+;;; off by K, then chasing down the list until the lead pointer falls off
+;;; the end.
+
+(define (take-right lis k)
+  (guarantee-index-fixnum k 'TAKE-RIGHT)
+  (let lp ((lag lis) (lead (%drop lis k)))
+    (if (pair? lead)
+	(lp (cdr lag) (cdr lead))
+	lag)))
+
+(define (drop-right lis k)
+  (guarantee-index-fixnum k 'DROP-RIGHT)
+  (let recur ((lag lis) (lead (%drop lis k)))
+    (if (pair? lead)
+	(cons (car lag) (recur (cdr lag) (cdr lead)))
+	'())))
+
+;;; In this function, LEAD is actually K+1 ahead of LAG. This lets
+;;; us stop LAG one step early, in time to smash its cdr to ().
+
+(define (drop-right! lis k)
+  (guarantee-index-fixnum k 'DROP-RIGHT!)
+  (let ((lead (%drop lis k)))
+    (if (pair? lead)
+	;; Standard case
+	(let lp ((lag lis) (lead (cdr lead)))
+	  (if (pair? lead)
+	      (lp (cdr lag) (cdr lead))
+	      (begin
+		(set-cdr! lag '())
+		lis)))
+	;; Special case dropping everything -- no cons to side-effect.
+	'())))
+
+(define (split-at x k)
+  (guarantee-index-fixnum k 'SPLIT-AT)
+  (let recur ((lis x) (k k))
+    (if (fix:> k 0)
+	(receive (prefix suffix) (recur (cdr lis) (fix:- k 1))
+	  (values (cons (car lis) prefix) suffix))
+	(values '() lis))))
+
+(define (split-at! x k)
+  (guarantee-index-fixnum k 'SPLIT-AT!)
+  (if (fix:> k 0)
+      (let* ((prev (%drop x (fix:- k 1)))
+	     (suffix (cdr prev)))
+	(set-cdr! prev '())
+	(values x suffix))
+      (values '() x)))
+
+;;;; Miscellaneous
+
+(define (length+ x)
+  (let lp ((x x) (lag x) (len 0))
+    (if (pair? x)
+	(let ((x (cdr x))
+	      (len (fix:+ len 1)))
+	  (if (pair? x)
+	      (let ((x (cdr x))
+		    (lag (cdr lag))
+		    (len (fix:+ len 1)))
+		(if (eq? x lag)
+		    #f
+		    (lp x lag len)))
+	      len))
+	len)))
+
+(define (append-reverse rev-head tail)
+  (let lp ((rev-head rev-head) (tail tail))
+    (if (null-list? rev-head 'APPEND-REVERSE)
+	tail
+	(lp (cdr rev-head) (cons (car rev-head) tail)))))
+
+(define (append-reverse! rev-head tail)
+  (let lp ((rev-head rev-head) (tail tail))
+    (if (null-list? rev-head 'APPEND-REVERSE!)
+	tail
+	(let ((next-rev (cdr rev-head)))
+	  (set-cdr! rev-head tail)
+	  (lp next-rev rev-head)))))
+
+(define (concatenate lists)
+  (reduce-right append '() lists))
+
+(define (concatenate! lists)
+  (reduce-right append! '() lists))
+
+(define (count pred list1 . lists)
+  (if (pair? lists)
+      (let lp ((list1 list1) (lists lists) (i 0))
+	(if (null-list? list1 'COUNT)
+	    i
+	    (receive (as ds) (%cars+cdrs lists)
+	      (if (null? as)
+		  i
+		  (lp (cdr list1)
+		      ds
+		      (if (apply pred (car list1) as)
+			  (fix:+ i 1)
+			  i))))))
+      (count-matching-items list1 pred)))
+
+(define (zip list1 . more-lists)
+  (apply map list list1 more-lists))
+
+(define (unzip1 lis)
+  (map car lis))
+
+(define (unzip2 lis)
+  (let recur ((lis lis))
+    (if (null-list? lis 'UNZIP2)
+	(values lis lis)
+	(let ((elt (car lis)))
+	  (receive (a b) (recur (cdr lis))
+	    (values (cons (car elt) a)
+		    (cons (cadr elt) b)))))))
+
+(define (unzip3 lis)
+  (let recur ((lis lis))
+    (if (null-list? lis 'UNZIP3)
+	(values lis lis lis)
+	(let ((elt (car lis)))
+	  (receive (a b c) (recur (cdr lis))
+	    (values (cons (car elt) a)
+		    (cons (cadr elt) b)
+		    (cons (caddr elt) c)))))))
+
+(define (unzip4 lis)
+  (let recur ((lis lis))
+    (if (null-list? lis 'UNZIP4)
+	(values lis lis lis lis)
+	(let ((elt (car lis)))
+	  (receive (a b c d) (recur (cdr lis))
+	    (values (cons (car elt) a)
+		    (cons (cadr elt) b)
+		    (cons (caddr elt) c)
+		    (cons (cadddr elt) d)))))))
+
+(define (unzip5 lis)
+  (let recur ((lis lis))
+    (if (null-list? lis 'UNZIP5)
+	(values lis lis lis lis lis)
+	(let ((elt (car lis)))
+	  (receive (a b c d e) (recur (cdr lis))
+	    (values (cons (car elt) a)
+		    (cons (cadr elt) b)
+		    (cons (caddr elt) c)
+		    (cons (cadddr elt) d)
+		    (cons (car (cddddr elt)) e)))))))
+
+(define (unfold p f g seed #!optional tail-gen)
+  (let recur ((seed seed))
+    (if (p seed)
+	(if (default-object? tail-gen) '() (tail-gen seed))
+	(cons (f seed) (recur (g seed))))))
+
+(define (unfold-right p f g seed #!optional tail)
+  (let lp
+      ((seed seed)
+       (ans (if (default-object? tail) '() tail)))
+    (if (p seed)
+	ans
+	(lp (g seed)
+	    (cons (f seed) ans)))))
+
+(define (pair-fold f zero lis1 . lists)
+  (if (pair? lists)
+      (let lp ((lists (cons lis1 lists)) (ans zero))
+	(let ((tails (%cdrs lists)))
+	  (if (null? tails)
+	      ans
+	      (lp tails (apply f (append! lists (list ans)))))))
+      (let lp ((lis lis1) (ans zero))
+	(if (null-list? lis 'PAIR-FOLD)
+	    ans
+	    ;; Grab the cdr now, in case F SET-CDR!s LIS.
+	    (let ((tail (cdr lis)))
+	      (lp tail
+		  (f lis ans)))))))
+
+(define (pair-fold-right f zero lis1 . lists)
+  (if (pair? lists)
+      (let recur ((lists (cons lis1 lists)))
+	(let ((cdrs (%cdrs lists)))
+	  (if (null? cdrs)
+	      zero
+	      (apply f (append! lists (list (recur cdrs)))))))
+      (let recur ((lis lis1))
+	(if (null-list? lis 'PAIR-FOLD-RIGHT)
+	    zero
+	    (f lis (recur (cdr lis)))))))
+
+(define (pair-for-each proc lis1 . lists)
+  (if (pair? lists)
+      (let lp ((lists (cons lis1 lists)))
+	(let ((tails (%cdrs lists)))
+	  (if (pair? tails)
+	      (begin
+		(apply proc lists)
+		(lp tails)))))
+      (let lp ((lis lis1))
+	(if (not (null-list? lis 'PAIR-FOR-EACH))
+	    ;; Grab the cdr now, in case PROC SET-CDR!s LIS.
+	    (let ((tail (cdr lis)))
+	      (proc lis)
+	      (lp tail))))))
+
+;;; We stop when LIS1 runs out, not when any list runs out.
+
+(define (map! f lis1 . lists)
+  (if (pair? lists)
+      (let lp ((lis1 lis1) (lists lists))
+	(if (not (null-list? lis1 'MAP!))
+	    (receive (heads tails) (%cars+cdrs/no-test lists)
+	      (set-car! lis1 (apply f (car lis1) heads))
+	      (lp (cdr lis1) tails))))
+      (pair-for-each (lambda (pair) (set-car! pair (f (car pair))))
+		     lis1))
+  lis1)
+
+;;; Map F across L, and save up all the non-false results.
+
+(define (filter-map f lis1 . lists)
+  (if (pair? lists)
+      (let recur ((lists (cons lis1 lists)))
+	(receive (cars cdrs) (%cars+cdrs lists)
+	  (if (pair? cars)
+	      (cond ((apply f cars) => (lambda (x) (cons x (recur cdrs))))
+		    (else (recur cdrs))) ; Tail call in this arm.
+	      '())))
+      (let recur ((lis lis1))
+	(if (null-list? lis 'FILTER-MAP)
+	    lis
+	    (let ((tail (recur (cdr lis))))
+	      (cond ((f (car lis)) => (lambda (x) (cons x tail)))
+		    (else tail)))))))
+
+;;; Map 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 MAP.
+
+(define (map-in-order f lis1 . lists)
+  (if (pair? lists)
+      (let recur ((lists (cons lis1 lists)))
+	(receive (cars cdrs) (%cars+cdrs lists)
+	  (if (pair? cars)
+	      ;; Do head first, then tail.
+	      (let ((x (apply f cars)))
+		(cons x (recur cdrs)))
+	      '())))
+      (let recur ((lis lis1))
+	(if (null-list? lis 'MAP-IN-ORDER)
+	    lis
+	    ;; Do head first, then tail.
+	    (let ((x (f (car lis))))
+	      (cons x
+		    (recur (cdr lis))))))))
+
+;;;; filter, remove, partition
+
+;;; FILTER, REMOVE, PARTITION and their destructive counterparts do not
+;;; disorder the elements of their argument.
+
+;; This FILTER shares the longest tail of L that has no deleted elements.
+;; If Scheme had multi-continuation calls, they could be made more efficient.
+
+;; Sleazing with EQ? makes this one faster.
+
+(define (filter pred lis)
+  (let recur ((lis lis))
+    (if (null-list? lis 'FILTER)
+	lis
+	(let ((head (car lis))
+	      (tail (cdr lis)))
+	  (if (pred head)
+	      (let ((new-tail (recur tail)))	; Replicate the RECUR call so
+		(if (eq? tail new-tail) lis
+		    (cons head new-tail)))
+	      (recur tail))))))			; this one can be a tail call.
+
+;;; This implementation of FILTER!
+;;; - doesn't cons, and uses no stack;
+;;; - is careful not to do redundant SET-CDR! writes, as writes to memory are
+;;;   usually expensive on modern machines, and can be extremely expensive on
+;;;   modern Schemes (e.g., ones that have generational GC's).
+;;; It just zips down contiguous runs of in and out elts in LIS doing the
+;;; minimal number of SET-CDR!s to splice the tail of one run of ins to the
+;;; beginning of the next.
+
+(define (filter! pred lis)
+  (let lp ((ans lis))
+    (cond ((null-list? ans 'FILTER!) ans) ; Scan looking for
+	  ((not (pred (car ans))) (lp (cdr ans)))	; first cons of result.
+
+	  ;; ANS is the eventual answer.
+	  ;; SCAN-IN: (CDR PREV) = LIS and (CAR PREV) satisfies PRED.
+	  ;;          Scan over a contiguous segment of the list that
+	  ;;          satisfies PRED.
+	  ;; SCAN-OUT: (CAR PREV) satisfies PRED. Scan over a contiguous
+	  ;;           segment of the list that *doesn't* satisfy PRED.
+	  ;;           When the segment ends, patch in a link from PREV
+	  ;;           to the start of the next good segment, and jump to
+	  ;;           SCAN-IN.
+	  (else (letrec ((scan-in (lambda (prev lis)
+				    (if (pair? lis)
+					(if (pred (car lis))
+					    (scan-in lis (cdr lis))
+					    (scan-out prev (cdr lis))))))
+			 (scan-out (lambda (prev lis)
+				     (let lp ((lis lis))
+				       (if (pair? lis)
+					   (if (pred (car lis))
+					       (begin (set-cdr! prev lis)
+						      (scan-in lis (cdr lis)))
+					       (lp (cdr lis)))
+					   (set-cdr! prev lis))))))
+		  (scan-in ans (cdr ans))
+		  ans)))))
+
+;;; Answers share common tail with LIS where possible;
+;;; the technique is slightly subtle.
+
+(define (partition pred lis)
+  (let recur ((lis lis))
+    (if (null-list? lis 'PARTITION)
+	(values lis lis)
+	(let ((elt (car lis))
+	      (tail (cdr lis)))
+	  (receive (in out) (recur tail)
+	    (if (pred elt)
+		(values (if (pair? out) (cons elt in) lis) out)
+		(values in (if (pair? in) (cons elt out) lis))))))))
+
+;;; This implementation of PARTITION!
+;;; - doesn't cons, and uses no stack;
+;;; - is careful not to do redundant SET-CDR! writes, as writes to memory are
+;;;   usually expensive on modern machines, and can be extremely expensive on
+;;;   modern Schemes (e.g., ones that have generational GC's).
+;;; It just zips down contiguous runs of in and out elts in LIS doing the
+;;; minimal number of SET-CDR!s to splice these runs together into the result
+;;; lists.
+
+(define (partition! pred lis)
+  (if (null-list? lis 'PARTITION!)
+      (values lis lis)
+
+      ;; This pair of loops zips down contiguous in & out runs of the
+      ;; list, splicing the runs together. The invariants are
+      ;;   SCAN-IN:  (cdr in-prev)  = LIS.
+      ;;   SCAN-OUT: (cdr out-prev) = LIS.
+      (letrec ((scan-in (lambda (in-prev out-prev lis)
+			  (let lp ((in-prev in-prev) (lis lis))
+			    (if (pair? lis)
+				(if (pred (car lis))
+				    (lp lis (cdr lis))
+				    (begin (set-cdr! out-prev lis)
+					   (scan-out in-prev lis (cdr lis))))
+				(set-cdr! out-prev lis))))) ; Done.
+
+	       (scan-out (lambda (in-prev out-prev lis)
+			   (let lp ((out-prev out-prev) (lis lis))
+			     (if (pair? lis)
+				 (if (pred (car lis))
+				     (begin (set-cdr! in-prev lis)
+					    (scan-in lis out-prev (cdr lis)))
+				     (lp lis (cdr lis)))
+				 (set-cdr! in-prev lis)))))) ; Done.
+
+	;; Crank up the scan&splice loops.
+	(if (pred (car lis))
+	    ;; LIS begins in-list. Search for out-list's first pair.
+	    (let lp ((prev-l lis) (l (cdr lis)))
+	      (cond ((not (pair? l)) (values lis l))
+		    ((pred (car l)) (lp l (cdr l)))
+		    (else (scan-out prev-l l (cdr l))
+			  (values lis l))))	; Done.
+
+	    ;; LIS begins out-list. Search for in-list's first pair.
+	    (let lp ((prev-l lis) (l (cdr lis)))
+	      (cond ((not (pair? l)) (values l lis))
+		    ((pred (car l))
+		     (scan-in l prev-l (cdr l))
+		     (values l lis))		; Done.
+		    (else (lp l (cdr l)))))))))
+
+(define-integrable (remove  pred l) (filter  (lambda (x) (not (pred x))) l))
+(define-integrable (remove! pred l) (filter! (lambda (x) (not (pred x))) l))
+
+;;;; Right-duplicate deletion
+
+;;; delete-duplicates delete-duplicates!
+;;;
+;;; Beware -- these are N^2 algorithms. To efficiently remove duplicates
+;;; in long lists, sort the list to bring duplicates together, then use a
+;;; linear-time algorithm to kill the dups. Or use an algorithm based on
+;;; element-marking. The former gives you O(n lg n), the latter is linear.
+
+(define (delete-duplicates lis #!optional elt=)
+  (let ((elt= (if (default-object? elt=) equal? elt=)))
+    (let recur ((lis lis))
+      (if (null-list? lis 'DELETE-DUPLICATES)
+	  lis
+	  (let* ((x (car lis))
+		 (tail (cdr lis))
+		 (new-tail (recur (delete x tail elt=))))
+	    (if (eq? tail new-tail) lis (cons x new-tail)))))))
+
+(define (delete-duplicates! lis #!optional elt=)
+  (let ((elt= (if (default-object? elt=) equal? elt=)))
+    (let recur ((lis lis))
+      (if (null-list? lis 'DELETE-DUPLICATES!)
+	  lis
+	  (let* ((x (car lis))
+		 (tail (cdr lis))
+		 (new-tail (recur (delete! x tail elt=))))
+	    (if (eq? tail new-tail) lis (cons x new-tail)))))))
+
+(define (find pred list)
+  (cond ((find-tail pred list) => car)
+	(else #f)))
+
+(define (find-tail pred list)
+  (let lp ((list list))
+    (and (not (null-list? list 'FIND-TAIL))
+	 (if (pred (car list)) list
+	     (lp (cdr list))))))
+
+(define (take-while pred lis)
+  (let recur ((lis lis))
+    (if (null-list? lis 'TAKE-WHILE)
+	'()
+	(let ((x (car lis)))
+	  (if (pred x)
+	      (cons x (recur (cdr lis)))
+	      '())))))
+
+(define (drop-while pred lis)
+  (let lp ((lis lis))
+    (if (null-list? lis 'DROP-WHILE)
+	'()
+	(if (pred (car lis))
+	    (lp (cdr lis))
+	    lis))))
+
+(define (take-while! pred lis)
+  (if (or (null-list? lis 'TAKE-WHILE!)
+	  (not (pred (car lis))))
+      '()
+      (begin
+	(let lp ((prev lis) (rest (cdr lis)))
+	  (if (pair? rest)
+	      (let ((x (car rest)))
+		(if (pred x) (lp rest (cdr rest))
+		    (set-cdr! prev '())))))
+	lis)))
+
+(define (span pred lis)
+  (let recur ((lis lis))
+    (if (null-list? lis 'SPAN)
+	(values '() '())
+	(let ((x (car lis)))
+	  (if (pred x)
+	      (receive (prefix suffix) (recur (cdr lis))
+		(values (cons x prefix) suffix))
+	      (values '() lis))))))
+
+(define (span! pred lis)
+  (if (or (null-list? lis 'SPAN!)
+	  (not (pred (car lis))))
+      (values '() lis)
+      (let ((suffix (let lp ((prev lis) (rest (cdr lis)))
+		      (if (null-list? rest 'SPAN!)
+			  rest
+			  (let ((x (car rest)))
+			    (if (pred x) (lp rest (cdr rest))
+				(begin (set-cdr! prev '())
+				       rest)))))))
+	(values lis suffix))))
+
+(define (break pred #!optional lis)
+  ;; This is a kludge to retain MIT/GNU Scheme's BREAK.
+  (if (default-object? lis)
+      (break-both pred)
+      (span (lambda (x) (not (pred x))) lis)))
+
+(define (break! pred lis)
+  (span! (lambda (x) (not (pred x))) lis))
+
+(define (any pred lis1 . lists)
+  (if (pair? lists)
+      (receive (heads tails) (%cars+cdrs (cons lis1 lists))
+	(and (pair? heads)
+	     (let lp ((heads heads) (tails tails))
+	       (receive (next-heads next-tails) (%cars+cdrs tails)
+		 (if (pair? next-heads)
+		     (or (apply pred heads)
+			 (lp next-heads next-tails))
+		     (apply pred heads))))))
+      (and (not (null-list? lis1 'ANY))
+	   (let lp ((head (car lis1)) (tail (cdr lis1)))
+	     (if (null-list? tail 'ANY)
+		 (pred head)
+		 (or (pred head)
+		     (lp (car tail) (cdr tail))))))))
+
+(define (every pred lis1 . lists)
+  (if (pair? lists)
+      (receive (heads tails) (%cars+cdrs (cons lis1 lists))
+	(or (not (pair? heads))
+	    (let lp ((heads heads) (tails tails))
+	      (receive (next-heads next-tails) (%cars+cdrs tails)
+		(if (pair? next-heads)
+		    (and (apply pred heads)
+			 (lp next-heads next-tails))
+		    (apply pred heads))))))
+      (or (null-list? lis1 'EVERY)
+	  (let lp ((head (car lis1)) (tail (cdr lis1)))
+	    (if (null-list? tail 'EVERY)
+		(pred head)
+		(and (pred head)
+		     (lp (car tail) (cdr tail))))))))
+
+(define (list-index pred lis1 . lists)
+  (if (pair? lists)
+      (let lp ((lists (cons lis1 lists)) (n 0))
+	(receive (heads tails) (%cars+cdrs lists)
+	  (and (pair? heads)
+	       (if (apply pred heads) n
+		   (lp tails (fix:+ n 1))))))
+      (let lp ((lis lis1) (n 0))
+	(and (not (null-list? lis 'LIST-INDEX))
+	     (if (pred (car lis))
+		 n
+		 (lp (cdr lis) (fix:+ n 1)))))))
+
+;;;; Lists-as-sets
+
+;;; This is carefully tuned code; do not modify casually.
+;;; - It is careful to share storage when possible;
+;;; - Side-effecting code tries not to perform redundant writes.
+;;; - It tries to avoid linear-time scans in special cases where constant-time
+;;;   computations can be performed.
+;;; - It relies on similar properties from the other list-lib procs it calls.
+;;;   For example, it uses the fact that the implementations of MEMBER and
+;;;   FILTER in this source code share longest common tails between args
+;;;   and results to get structure sharing in the lset procedures.
+
+(define (%lset2<= = lis1 lis2)
+  (every (lambda (x) (member x lis2 =)) lis1))
+
+(define (lset<= = . lists)
+  (or (not (pair? lists)) ; 0-ary case
+      (let lp ((s1 (car lists)) (rest (cdr lists)))
+	(or (not (pair? rest))
+	    (let ((s2 (car rest))  (rest (cdr rest)))
+	      (and (or (eq? s2 s1)	; Fast path
+		       (%lset2<= = s1 s2)) ; Real test
+		   (lp s2 rest)))))))
+
+(define (lset= = . lists)
+  (or (not (pair? lists)) ; 0-ary case
+      (let lp ((s1 (car lists)) (rest (cdr lists)))
+	(or (not (pair? rest))
+	    (let ((s2   (car rest))
+		  (rest (cdr rest)))
+	      (and (or (eq? s1 s2)	; Fast path
+		       (and (%lset2<= = s1 s2) (%lset2<= = s2 s1))) ; Real test
+		   (lp s2 rest)))))))
+
+(define (lset-adjoin = lis . elts)
+  (fold (lambda (elt ans) (if (member elt ans =) ans (cons elt ans)))
+	lis elts))
+
+(define (lset-union = . lists)
+  (reduce (lambda (lis ans)		; Compute ANS + LIS.
+	    (cond ((null? lis) ans)	; Don't copy any lists
+		  ((null? ans) lis) 	; if we don't have to.
+		  ((eq? lis ans) ans)
+		  (else
+		   (fold (lambda (elt ans) (if (any (lambda (x) (= x elt)) ans)
+					       ans
+					       (cons elt ans)))
+			 ans lis))))
+	  '() lists))
+
+(define (lset-union! = . lists)
+  (reduce (lambda (lis ans)
+	    ;; Splice new elts of LIS onto the front of ANS.
+	    (cond ((null? lis) ans)	; Don't copy any lists
+		  ((null? ans) lis) 	; if we don't have to.
+		  ((eq? lis ans) ans)
+		  (else
+		   (pair-fold (lambda (pair ans)
+				(let ((elt (car pair)))
+				  (if (any (lambda (x) (= x elt)) ans)
+				      ans
+				      (begin (set-cdr! pair ans) pair))))
+			      ans lis))))
+	  '()
+	  lists))
+
+(define (lset-intersection = lis1 . lists)
+  (let ((lists (delete lis1 lists eq?))) ; Throw out any LIS1 vals.
+    (cond ((any (lambda (list)
+		  (null-list? list 'LSET-INTERSECTION))
+		lists)
+	   '())		; Short cut
+	  ((null? lists)          lis1)		; Short cut
+	  (else (filter (lambda (x)
+			  (every (lambda (lis) (member x lis =)) lists))
+			lis1)))))
+
+(define (lset-intersection! = lis1 . lists)
+  (let ((lists (delete lis1 lists eq?))) ; Throw out any LIS1 vals.
+    (cond ((any (lambda (list)
+		  (null-list? list 'LSET-INTERSECTION!))
+		lists)
+	   '())		; Short cut
+	  ((null? lists)          lis1)		; Short cut
+	  (else (filter! (lambda (x)
+			   (every (lambda (lis) (member x lis =)) lists))
+			 lis1)))))
+
+(define (lset-difference = lis1 . lists)
+  (let ((lists (filter pair? lists)))	; Throw out empty lists.
+    (cond ((null? lists)     lis1)	; Short cut
+	  ((memq lis1 lists) '())	; Short cut
+	  (else (filter (lambda (x)
+			  (every (lambda (lis) (not (member x lis =)))
+				 lists))
+			lis1)))))
+
+(define (lset-difference! = lis1 . lists)
+  (let ((lists (filter pair? lists)))	; Throw out empty lists.
+    (cond ((null? lists)     lis1)	; Short cut
+	  ((memq lis1 lists) '())	; Short cut
+	  (else (filter! (lambda (x)
+			   (every (lambda (lis) (not (member x lis =)))
+				  lists))
+			 lis1)))))
+
+(define (lset-xor = . lists)
+  (reduce (lambda (b a)			; Compute A xor B:
+	    ;; Note that this code relies on the constant-time
+	    ;; short-cuts provided by LSET-DIFF+INTERSECTION,
+	    ;; LSET-DIFFERENCE & APPEND to provide constant-time short
+	    ;; cuts for the cases A = (), B = (), and A eq? B. It takes
+	    ;; a careful case analysis to see it, but it's carefully
+	    ;; built in.
+
+	    ;; Compute a-b and a^b, then compute b-(a^b) and
+	    ;; cons it onto the front of a-b.
+	    (receive (a-b a-int-b)   (lset-diff+intersection = a b)
+	      (cond ((null? a-b)     (lset-difference b a =))
+		    ((null? a-int-b) (append b a))
+		    (else (fold (lambda (xb ans)
+				  (if (member xb a-int-b =) ans (cons xb ans)))
+				a-b
+				b)))))
+	  '() lists))
+
+(define (lset-xor! = . lists)
+  (reduce (lambda (b a)			; Compute A xor B:
+	    ;; Note that this code relies on the constant-time
+	    ;; short-cuts provided by LSET-DIFF+INTERSECTION,
+	    ;; LSET-DIFFERENCE & APPEND to provide constant-time short
+	    ;; cuts for the cases A = (), B = (), and A eq? B. It takes
+	    ;; a careful case analysis to see it, but it's carefully
+	    ;; built in.
+
+	    ;; Compute a-b and a^b, then compute b-(a^b) and
+	    ;; cons it onto the front of a-b.
+	    (receive (a-b a-int-b)   (lset-diff+intersection! = a b)
+	      (cond ((null? a-b)     (lset-difference! b a =))
+		    ((null? a-int-b) (append! b a))
+		    (else (pair-fold (lambda (b-pair ans)
+				       (if (member (car b-pair) a-int-b =)
+					   ans
+					   (begin
+					     (set-cdr! b-pair ans)
+					     b-pair)))
+				     a-b
+				     b)))))
+	  '() lists))
+
+(define (lset-diff+intersection = lis1 . lists)
+  (cond ((every (lambda (list)
+		  (null-list? list 'LSET-DIFF+INTERSECTION))
+		lists)
+	 (values lis1 '()))	; Short cut
+	((memq lis1 lists)        (values '() lis1))	; Short cut
+	(else (partition (lambda (elt)
+			   (not (any (lambda (lis) (member elt lis =))
+				     lists)))
+			 lis1))))
+(define (lset-diff+intersection! = lis1 . lists)
+  (cond ((every (lambda (list)
+		  (null-list? list 'LSET-DIFF+INTERSECTION!))
+		lists)
+	 (values lis1 '()))	; Short cut
+	((memq lis1 lists)        (values '() lis1))	; Short cut
+	(else (partition! (lambda (elt)
+			    (not (any (lambda (lis) (member elt lis =))
+				      lists)))
+			  lis1))))
+
+;;;; Utilities
+
+;;; These little internal utilities are used by the general
+;;; fold & mapper funs for the n-ary cases.  It'd be nice if they got inlined.
+;;; One the other hand, the n-ary cases are painfully inefficient as it is.
+;;; An aggressive implementation should simply re-write these functions
+;;; for raw efficiency; I have written them for as much clarity, portability,
+;;; and simplicity as can be achieved.
+;;;
+;;; I use the dreaded call/cc to do local aborts. A good compiler could
+;;; handle this with extreme efficiency. An implementation that provides
+;;; a one-shot, non-persistent continuation grabber could help the compiler
+;;; out by using that in place of the call/cc's in these routines.
+;;;
+;;; These functions have funky definitions that are precisely tuned to
+;;; the needs of the fold/map procs -- for example, to minimize the number
+;;; of times the argument lists need to be examined.
+
+(define (%cdrs lists)
+  ;; Return (map cdr lists).
+  ;; However, if any element of LISTS is empty, just abort and return '().
+  (let loop ((lists lists) (cdrs '()))
+    (if (pair? lists)
+	(if (null-list? (car lists) #f)
+	    '()
+	    (loop (cdr lists)
+		  (cons (cdar lists) cdrs)))
+	(reverse! cdrs))))
+
+(define (%cars+ lists last-elt)
+  (let recur ((lists lists))
+    (if (pair? lists)
+	(cons (caar lists) (recur (cdr lists)))
+	(list last-elt))))
+
+;;; LISTS is a (not very long) non-empty list of lists.
+;;; Return two lists: the cars & the cdrs of the lists.
+;;; However, if any of the lists is empty, just abort and return [() ()].
+
+(define (%cars+cdrs lists)
+  (let loop ((lists lists) (cars '()) (cdrs '()))
+    (if (pair? lists)
+	(if (null-list? (car lists) #f)
+	    (values '() '())
+	    (loop (cdr lists)
+		  (cons (caar lists) cars)
+		  (cons (cdar lists) cdrs)))
+	(values (reverse! cars) (reverse! cdrs)))))
+
+;;; Like %CARS+CDRS, but we pass in a final elt tacked onto the end of the
+;;; cars list.  What a hack.
+
+(define (%cars+cdrs+ lists cars-final)
+  (let loop ((lists lists) (cars (list cars-final)) (cdrs '()))
+    (if (pair? lists)
+	(if (null-list? (car lists) #f)
+	    (values '() '())
+	    (loop (cdr lists)
+		  (cons (caar lists) cars)
+		  (cons (cdar lists) cdrs)))
+	(values (reverse! cars) (reverse! cdrs)))))
+
+;;; Like %CARS+CDRS, but blow up if any list is empty.
+(define (%cars+cdrs/no-test lists)
+  (let loop ((lists lists) (cars '()) (cdrs '()))
+    (if (pair? lists)
+	(loop (cdr lists)
+	      (cons (caar lists) cars)
+	      (cons (cdar lists) cdrs))
+	(values (reverse! cars) (reverse! cdrs)))))
\ No newline at end of file