From c1a677ca4bd48c0bd1341b325087ca10dcd41077 Mon Sep 17 00:00:00 2001
From: Abdulaziz Ghuloum <aghuloum@cs.indiana.edu>
Date: Sat, 15 Dec 2007 08:55:53 -0500
Subject: [PATCH] Changed implementation of append so that it uses half the
 cons cells that it previously used.  Interestingly, this reduced bootstrap
 time by 60ms and 2 garbage collections!  And I thought I did not use append
 :-).

---
 scheme/ikarus.lists.ss | 8 +++++---
 scheme/last-revision   | 2 +-
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/scheme/ikarus.lists.ss b/scheme/ikarus.lists.ss
index 32445de..9962e36 100644
--- a/scheme/ikarus.lists.ss
+++ b/scheme/ikarus.lists.ss
@@ -145,18 +145,20 @@
             (if (null? h)
                 ac 
                 (die 'append "not a proper list" ls)))))
-    (define revcons
+    (define rev!
       (lambda (ls ac)
         (cond
           [(null? ls) ac]
           [else
-           (revcons ($cdr ls) (cons ($car ls) ac))])))
+           (let ([ls^ ($cdr ls)])
+             ($set-cdr! ls ac)
+             (rev! ls^ ls))])))
     (define append1
       (lambda (ls ls*)
         (cond
           [(null? ls*) ls]
           [else 
-           (revcons (reverse ls ls ls '())
+           (rev! (reverse ls ls ls '())
               (append1 ($car ls*) ($cdr ls*)))])))
     (define append
       (case-lambda
diff --git a/scheme/last-revision b/scheme/last-revision
index 4c127d8..600fe59 100644
--- a/scheme/last-revision
+++ b/scheme/last-revision
@@ -1 +1 @@
-1246
+1248