From: Joe Marshall <edu/mit/csail/zurich/jrm>
Date: Tue, 22 Mar 1988 18:10:01 +0000 (+0000)
Subject: Make set/adjoin not cons so much.
X-Git-Tag: 20090517-FFI~12855
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=0af3b1724d77e36dd7ef0236cc8a0452103cc170;p=mit-scheme.git

Make set/adjoin not cons so much.
---

diff --git a/v7/src/sf/lsets.scm b/v7/src/sf/lsets.scm
index 7846189b9..e38c1789e 100644
--- a/v7/src/sf/lsets.scm
+++ b/v7/src/sf/lsets.scm
@@ -264,7 +264,9 @@ to figure out what is going on in this code.
 (define (adjoin-element predicate element list)
   (declare (integrate  list))
   predicate ; is ignored
-  (cons element (delq element list)))
+  (if (memq element list)
+      list
+      (cons element list)))
 
 (define (set/adjoin set element)
   (spread-set set