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diff lib/ur/list.ur @ 2095:d9f918b79b5a

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List.mem
author Adam Chlipala <adam@chlipala.net>
date Tue, 23 Dec 2014 14:41:23 -0500
parents 146ec8e90063
children
line wrap: on
line diff
--- a/lib/ur/list.ur	Tue Dec 23 13:42:20 2014 -0500
+++ b/lib/ur/list.ur	Tue Dec 23 14:41:23 2014 -0500
@@ -216,6 +216,16 @@
         fold []
     end
 
+fun mem [a] (_ : eq a) (x : a) =
+    let
+        fun mm ls =
+            case ls of
+                [] => False
+              | y :: ls => y = x || mm ls
+    in
+        mm
+    end
+
 fun find [a] f =
     let
         fun find' ls =