Mercurial > urweb

changeset 1519:ada582d07ae1

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List.find
author Adam Chlipala <adam@chlipala.net>
date Sun, 24 Jul 2011 15:47:09 -0400
parents 883347f5c3c2
children b5517f47b1f1
files lib/ur/list.ur lib/ur/list.urs
diffstat 2 files changed, 16 insertions(+), 0 deletions(-) [+]
line wrap: on
line diff
--- a/lib/ur/list.ur	Sun Jul 24 14:49:40 2011 -0400
+++ b/lib/ur/list.ur	Sun Jul 24 15:47:09 2011 -0400
@@ -206,6 +206,20 @@
         fold []
     end
 
+fun find [a] f =
+    let
+        fun find' ls =
+            case ls of
+                [] => None
+              | x :: ls =>
+                if f x then
+                    Some x
+                else
+                    find' ls
+    in
+        find'
+    end
+
 fun search [a] [b] f =
     let
         fun search' ls =
--- a/lib/ur/list.urs	Sun Jul 24 14:49:40 2011 -0400
+++ b/lib/ur/list.urs	Sun Jul 24 15:47:09 2011 -0400
@@ -44,6 +44,8 @@
 val foldlMap : a ::: Type -> b ::: Type -> c ::: Type
                -> (a -> b -> c * b) -> b -> t a -> t c * b
 
+val find : a ::: Type -> (a -> bool) -> t a -> option a
+
 val search : a ::: Type -> b ::: Type -> (a -> option b) -> t a -> option b
 
 val all : a ::: Type -> (a -> bool) -> t a -> bool