X-Git-Url: http://git.kpe.io/?p=kmrcl.git;a=blobdiff_plain;f=lists.lisp;h=a2ae23ff6c34d4c6ee20d0e2d7c1f426542d2018;hp=5cd193cefe96910174ef1c9a9a5039c0b1c9b7b5;hb=c0e985428b4aa14bdc5a0688315bc4dbb5142ba3;hpb=7397fb7597f3fe9c658e6fb1ad67c805029dd073

diff --git a/lists.lisp b/lists.lisp
index 5cd193c..a2ae23f 100644
--- a/lists.lisp
+++ b/lists.lisp
@@ -73,11 +73,14 @@
             it
             nil)))))
 
-(defun flatten (lis)
-  (cond ((atom lis) lis)
-        ((listp (car lis))
-         (append (flatten (car lis)) (flatten (cdr lis))))
-        (t (append (list (car lis)) (flatten (cdr lis))))))
+(defun flatten (tree)
+  (let ((result '()))
+    (labels ((scan (item)
+               (if (consp item)
+                   (map nil #'scan item)
+                   (push item result))))
+      (scan tree))
+    (nreverse result)))
 
 ;;; Keyword functions