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diff src/elab_util.sml @ 198:ab86aa858e6c

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'Option' datatype encoding
author Adam Chlipala <adamc@hcoop.net>
date Sat, 09 Aug 2008 19:23:31 -0400
parents aa54250f58ac
children dd82457fda82
line wrap: on
line diff
--- a/src/elab_util.sml	Sat Aug 09 16:54:04 2008 -0400
+++ b/src/elab_util.sml	Sat Aug 09 19:23:31 2008 -0400
@@ -30,10 +30,14 @@
 open Elab
 
 fun classifyDatatype xncs =
-    if List.all (fn (_, _, NONE) => true | _ => false) xncs then
-        Enum
-    else
-        Default
+    case xncs of
+        [(_, _, NONE), (_, _, SOME _)] => Option
+      | [(_, _, SOME _), (_, _, NONE)] => Option
+      | _ =>
+        if List.all (fn (_, _, NONE) => true | _ => false) xncs then
+            Enum
+        else
+            Default
 
 structure S = Search