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diff lib/ur/list.ur @ 1768:a613cae954ca

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Some standard library additions from Edward Z. Yang
author Adam Chlipala <adam@chlipala.net>
date Sat, 19 May 2012 11:32:12 -0400
parents f4cb4eebf7ae
children 146ec8e90063
line wrap: on
line diff
--- a/lib/ur/list.ur	Thu May 17 10:20:24 2012 -0400
+++ b/lib/ur/list.ur	Sat May 19 11:32:12 2012 -0400
@@ -424,3 +424,16 @@
 
 fun splitAt [a] (n : int) (xs : list a) : list a * list a =
     (take n xs, drop n xs)
+
+fun mapXiM [m ::: Type -> Type] (_ : monad m) [a] [ctx ::: {Unit}] (f : int -> a -> m (xml ctx [] [])) : t a -> m (xml ctx [] []) =
+    let
+        fun mapXiM' i ls =
+            case ls of
+                [] => return <xml/>
+              | x :: ls =>
+                this <- f i x;
+                rest <- mapXiM' (i+1) ls;
+                return <xml>{this}{rest}</xml>
+    in
+        mapXiM' 0
+    end