From: Mark Wooding <mdw@distorted.org.uk>
Date: Wed, 17 May 2006 18:40:14 +0000 (+0100)
Subject: base: New `until' macro does the obvious thing.
X-Git-Url: https://git.distorted.org.uk/~mdw/lisp/commitdiff_plain/38ccae7f2e8fdae39c9c3c2990b90c990a1489de

base: New `until' macro does the obvious thing.
---

diff --git a/mdw-base.lisp b/mdw-base.lisp
index 37a3068..e87c511 100644
--- a/mdw-base.lisp
+++ b/mdw-base.lisp
@@ -33,7 +33,7 @@
 	   #:stringify #:mappend #:listify #:fix-pair #:pairify #:parse-body
 	   #:whitespace-char-p
 	   #:slot-uninitialized
-	   #:nlet #:while #:case2 #:ecase2
+	   #:nlet #:while #:until #:case2 #:ecase2
 	   #:with-gensyms #:let*/gensyms #:with-places
 	   #:locp #:locf #:ref #:with-locatives
 	   #:update-place #:update-place-after
@@ -189,9 +189,11 @@
 
 (defmacro while (cond &body body)
   "If COND is false, evaluate to nil; otherwise evaluate BODY and try again."
-  `(loop
-     (unless ,cond (return))
-     ,@body))
+  `(loop (unless ,cond (return)) (progn ,@body)))
+
+(defmacro until (cond &body body)
+  "If COND is true, evaluate to nil; otherwise evaluate BODY and try again."
+  `(loop (when ,cond (return)) (progn ,@body)))
 
 (compile-time-defun do-case2-like (kind vform clauses)
   "Helper function for `case2' and `ecase2'."