From 5d0416aec9531a0a9797d3c3290f7b7ca9de4016 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Thu, 9 Apr 2009 00:58:13 +0000
Subject: [PATCH] David's build-list

svn: r14472
---
 collects/scheme/private/list.ss | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/collects/scheme/private/list.ss b/collects/scheme/private/list.ss
index a5202a47f8..bd3dc7565c 100644
--- a/collects/scheme/private/list.ss
+++ b/collects/scheme/private/list.ss
@@ -225,13 +225,10 @@
     (unless (and (procedure? fcn)
                  (procedure-arity-includes? fcn 1))
       (raise-type-error 'build-list "procedure (arity 1)" fcn))
-    (if (zero? n)
-      '()
-      (let loop ([i 0] [a null])
-        (if (= i n)
-            (reverse a)
-            (loop (add1 i)
-                  (cons (fcn i) a))))))
+    (let recr ([j 0] [i n])
+      (cond [(zero? i) null]
+            [else (cons (fcn j)
+                        (recr (add1 j) (sub1 i)))])))
 
   (define compose
     (case-lambda