From 4f2c619bb0971153c518f120c8911ce3a94f783d Mon Sep 17 00:00:00 2001
From: Adam Chlipala <adam@chlipala.net>
Date: Sun, 21 Nov 2010 15:43:24 -0500
Subject: Fix a bug in C list unurlification

---
 lib/ur/list.ur | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

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

diff --git a/lib/ur/list.ur b/lib/ur/list.ur
index 71d8fa98..354ef132 100644
--- a/lib/ur/list.ur
+++ b/lib/ur/list.ur
@@ -308,6 +308,20 @@ fun sort [a] (gt : a -> a -> bool) (ls : t a) : t a =
         sort' ls
     end
 
+val nth [a] =
+    let
+        fun nth (ls : list a) (n : int) : option a =
+            case ls of
+                [] => None
+              | x :: ls' =>
+                if n <= 0 then
+                    Some x
+                else
+                    nth ls' (n-1)
+    in
+        nth
+    end
+
 fun assoc [a] [b] (_ : eq a) (x : a) =
     let
         fun assoc' (ls : list (a * b)) =
-- 
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