From 5f341ee6866e51c5f528084d601678b91a0d6908 Mon Sep 17 00:00:00 2001
From: Adam Chlipala <adamc@hcoop.net>
Date: Sun, 13 Jun 2010 14:13:47 -0400
Subject: List.mapi

---
 lib/ur/list.ur  | 10 ++++++++++
 lib/ur/list.urs |  2 ++
 2 files changed, 12 insertions(+)

diff --git a/lib/ur/list.ur b/lib/ur/list.ur
index bccbc82a..bb814714 100644
--- a/lib/ur/list.ur
+++ b/lib/ur/list.ur
@@ -101,6 +101,16 @@ fun mp [a] [b] f =
         mp' []
     end
 
+fun mapi [a] [b] f =
+    let
+        fun mp' n acc ls =
+            case ls of
+                [] => rev acc
+              | x :: ls => mp' (n + 1) (f n x :: acc) ls
+    in
+        mp' 0 []
+    end
+
 fun mapPartial [a] [b] f =
     let
         fun mp' acc ls =
diff --git a/lib/ur/list.urs b/lib/ur/list.urs
index 00c95053..7ce3c61f 100644
--- a/lib/ur/list.urs
+++ b/lib/ur/list.urs
@@ -22,6 +22,8 @@ val mp : a ::: Type -> b ::: Type -> (a -> b) -> t a -> t b
 
 val mapPartial : a ::: Type -> b ::: Type -> (a -> option b) -> t a -> t b
 
+val mapi : a ::: Type -> b ::: Type -> (int -> a -> b) -> t a -> t b
+
 val mapX : a ::: Type -> ctx ::: {Unit} -> (a -> xml ctx [] []) -> t a -> xml ctx [] []
 
 val mapM : m ::: (Type -> Type) -> monad m -> a ::: Type -> b ::: Type
-- 
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