From: Kevin M. Rosenberg <kevin@rosenberg.net>
Date: Sat, 28 Aug 2004 02:15:20 +0000 (+0000)
Subject: r9935: fix update-alist
X-Git-Tag: v1.96~63
X-Git-Url: http://git.kpe.io/?p=kmrcl.git;a=commitdiff_plain;h=7446fd15be7c6b489b347d47526eb973f9ed7438

r9935: fix update-alist
---

diff --git a/lists.lisp b/lists.lisp
index 3115dd5..9793f27 100644
--- a/lists.lisp
+++ b/lists.lisp
@@ -151,19 +151,24 @@
 
 (defmacro update-alist (akey value alist &key (test '#'eql) (key '#'identity))
   "Macro to support below (setf get-alist)"
-  (let ((elem (gensym)))
-    `(let ((,elem (assoc ,akey ,alist :test ,test :key ,key)))
-       (if ,elem
-	   (progn
-	     (setf (cdr ,elem) ,value)
-	     ,alist)
-	 (setf ,alist (acons ,akey ,value ,alist))))))
+  (let ((elem (gensym "ELEM-"))
+	(val (gensym "VAL-")))
+    `(let ((,elem (assoc ,akey ,alist :test ,test :key ,key))
+	   (,val ,value))
+       (cond
+	(,elem
+	 (setf (cdr ,elem) ,val))
+	(,alist
+	 (setf (cdr (last ,alist)) (list (cons ,akey ,val))))
+	 (t
+	  (setf ,alist (list (cons ,akey ,val)))))
+       ,alist)))
 
 (defun get-alist (key alist &key (test #'eql))
   (cdr (assoc key alist :test test)))
 
 (defun (setf get-alist) (value key alist &key (test #'eql))
-  "This doesn't work to add a field which alist value is only modified locally"
+  "This won't work if the alist is NIL."
   (update-alist key value alist :test test)
   value)