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From: Kevin Ryde <user42@zip.com.au>
Subject: srfi-1 circular-list
Date: Sat, 20 Mar 2004 08:11:27 +1000	[thread overview]
Message-ID: <87fzc4h4hc.fsf@zip.com.au> (raw)

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        * srfi-1.scm (circular-list): Rewrite using set-cdr!, no need to copy
        parameter list.


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--- srfi-1.scm.~1.31.~	2003-12-03 07:14:46.000000000 +1000
+++ srfi-1.scm	2004-03-18 14:59:56.000000000 +1000
@@ -1,6 +1,6 @@
 ;;; srfi-1.scm --- List Library
 
-;; 	Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
+;; 	Copyright (C) 2001, 2002, 2003, 2004 Free Software Foundation, Inc.
 ;;
 ;; This library is free software; you can redistribute it and/or
 ;; modify it under the terms of the GNU Lesser General Public
@@ -247,16 +247,10 @@
       acc
       (lp (- n 1) (cons (init-proc (- n 1)) acc)))))
 
-(define (circular-list elt1 . rest)
-  (let ((start (cons elt1 '())))
-    (let lp ((r rest) (p start))
-      (if (null? r)
-	(begin
-	  (set-cdr! p start)
-	  start)
-	(begin
-	  (set-cdr! p (cons (car r) '()))
-	  (lp (cdr r) (cdr p)))))))
+(define (circular-list . lst)
+  (if (not (null? lst))
+      (set-cdr! (last-pair lst) lst))
+  lst)
 
 (define (iota count . rest)
   (check-arg-type non-negative-integer? count "iota")

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             reply	other threads:[~2004-03-19 22:11 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2004-03-19 22:11 Kevin Ryde [this message]
2004-03-19 22:24 ` srfi-1 circular-list Paul Jarc
2004-03-19 22:32   ` Kevin Ryde

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