From df475a9256347564d3adc1fafc53c4d93b4e73f7 Mon Sep 17 00:00:00 2001
From: Adam Chlipala <adam@chlipala.net>
Date: Sat, 19 May 2012 11:32:12 -0400
Subject: Some standard library additions from Edward Z. Yang

---
 lib/ur/list.ur | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'lib/ur/list.ur')

diff --git a/lib/ur/list.ur b/lib/ur/list.ur
index 2d5addc9..bce5335e 100644
--- a/lib/ur/list.ur
+++ b/lib/ur/list.ur
@@ -424,3 +424,16 @@ fun drop [a] (n : int) (xs : list a) : list a =
 
 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
-- 
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