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Add an example of the use of unfoldr, following doc feedback from dozer
author
Don Stewart
<dons@cse.unsw.edu.au>
Fri, 24 Nov 2006 01:12:49 +0000
(
01:12
+0000)
committer
Don Stewart
<dons@cse.unsw.edu.au>
Fri, 24 Nov 2006 01:12:49 +0000
(
01:12
+0000)
Data/List.hs
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diff --git
a/Data/List.hs
b/Data/List.hs
index
2ce489d
..
b6a847b
100644
(file)
--- a/
Data/List.hs
+++ b/
Data/List.hs
@@
-855,7
+855,12
@@
rqpart cmp x (y:ys) rle rgt r =
--
-- > f' (f x y) = Just (x,y)
-- > f' z = Nothing
-
+--
+-- A simple use of unfoldr:
+--
+-- > unfoldr (\b -> if b == 0 then Nothing else Just (b, b-1)) 10
+-- > [10,9,8,7,6,5,4,3,2,1]
+--
unfoldr :: (b -> Maybe (a, b)) -> b -> [a]
unfoldr f b =
case f b of