X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/lisp/blobdiff_plain/f4df6cf47a48e12e3e18d3d2a6285147f6f1c147..4b6a6387f82f1bb2058d642dcbd7040ce2578cea:/mdw-base.lisp?ds=sidebyside

diff --git a/mdw-base.lisp b/mdw-base.lisp
index 0b68b8d..59ea692 100644
--- a/mdw-base.lisp
+++ b/mdw-base.lisp
@@ -30,7 +30,7 @@ (defpackage #:mdw.base
   (:use #:common-lisp)
   (:export #:compile-time-defun
 	   #:show
-	   #:stringify #:listify #:fix-pair #:pairify #:parse-body
+	   #:stringify #:mappend #:listify #:fix-pair #:pairify #:parse-body
 	   #:whitespace-char-p
 	   #:slot-uninitialized
 	   #:nlet #:while #:case2 #:ecase2
@@ -69,6 +69,12 @@ (defun stringify (str)
     (t (with-output-to-string (s)
 	 (princ str s)))))
 
+(defun mappend (function list &rest more-lists)
+  "Apply FUNCTION to corresponding elements of LIST and MORE-LISTS, yielding
+   a list.  Return the concatenation of all the resulting lists.  Like
+   mapcan, but nondestructive."
+  (apply #'append (apply #'mapcar function list more-lists)))
+
 (compile-time-defun listify (x)
   "If X is a (possibly empty) list, return X; otherwise return (list X)."
   (if (listp x) x (list x)))