X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~mdw/git/lisp/blobdiff_plain/00b2180928c51dd6ca8e767d5b752718c4ca4ab9..a035dd4a8175317f19a35cd04568d1655fb8d417:/mdw-base.lisp

diff --git a/mdw-base.lisp b/mdw-base.lisp
index e87c511..c4c3e17 100644
--- a/mdw-base.lisp
+++ b/mdw-base.lisp
@@ -28,7 +28,8 @@
 
 (defpackage #:mdw.base
   (:use #:common-lisp)
-  (:export #:compile-time-defun
+  (:export #:unsigned-fixnum
+	   #:compile-time-defun
 	   #:show
 	   #:stringify #:mappend #:listify #:fix-pair #:pairify #:parse-body
 	   #:whitespace-char-p
@@ -43,6 +44,13 @@ (defpackage #:mdw.base
 
 (in-package #:mdw.base)
 
+;;;--------------------------------------------------------------------------
+;;; Useful types.
+
+(deftype unsigned-fixnum ()
+  "Unsigned fixnums; useful as array indices and suchlike."
+  `(mod ,most-positive-fixnum))
+
 ;;;--------------------------------------------------------------------------
 ;;; Some simple macros to get things going.