base: Export unsigned-fixnum as a handy type to have.

diff --git a/mdw-base.lisp b/mdw-base.lisp
index e87c51191ab1e155c07758839b8b1c9ba26c7efc..c4c3e1748224af8bb00c0c73d3aa98363880ca71 100644 (file)
--- 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.