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[project @ 2003-05-13 11:42:47 by simonpj]
author
simonpj
<unknown>
Tue, 13 May 2003 11:42:47 +0000
(11:42 +0000)
committer
simonpj
<unknown>
Tue, 13 May 2003 11:42:47 +0000
(11:42 +0000)
Generalise the type of listens slightly; a suggestion from Tom Pledger
Control/Monad/Writer.hs
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diff --git
a/Control/Monad/Writer.hs
b/Control/Monad/Writer.hs
index
79ec97e
..
b941e65
100644
(file)
--- a/
Control/Monad/Writer.hs
+++ b/
Control/Monad/Writer.hs
@@
-59,7
+59,7
@@
class (Monoid w, Monad m) => MonadWriter w m | m -> w where
listen :: m a -> m (a, w)
pass :: m (a, w -> w) -> m a
-listens :: (MonadWriter w m) => (w -> w) -> m a -> m (a, w)
+listens :: (MonadWriter w m) => (w -> b) -> m a -> m (a, b)
listens f m = do
(a, w) <- listen m
return (a, f w)