From: Vladimir Sedach <vsedach@gmail.com>
Date: Mon, 8 Jun 2009 04:35:05 +0000 (-0600)
Subject: Fixed 'flatten' to correctly handle lists with non-nil cdr (ie '(1 . 2)).
X-Git-Url: https://git.hcoop.net/clinton/parenscript.git/commitdiff_plain/604b5bbea9dd9eff7a21a59f2236f0d9374a13db

Fixed 'flatten' to correctly handle lists with non-nil cdr (ie '(1 . 2)).

Thanks to Scott Bell for the bug report.
http://common-lisp.net/pipermail/parenscript-devel/2009-June/000528.html
---

diff --git a/src/utils.lisp b/src/utils.lisp
index de77d42..9047abb 100644
--- a/src/utils.lisp
+++ b/src/utils.lisp
@@ -99,7 +99,7 @@ SOMEGLOBAL."
           ,(let (,@(loop for n in names for g in gensyms collect `(,n ,g)))
                 ,@body)))))
 
-(defun flatten (x)
-  (if (atom x)
-      (list x)
-      (mapcan #'flatten x)))
+(defun flatten (x &optional acc)
+  (cond ((null x) acc)
+        ((atom x) (cons x acc))
+        (t (flatten (car x) (flatten (cdr x) acc)))))