[commit: base] master: Move the munzip function in the Zip type class; (2ceacbc)

[Simon Peyton Jones]

Repository : ssh://darcs.haskell.org//srv/darcs/packages/base

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/2ceacbc35d9c5f4bc6cbcfa46f64d333f9dc53c7

>---------------------------------------------------------------

commit 2ceacbc35d9c5f4bc6cbcfa46f64d333f9dc53c7
Author: George Giorgidze <giorgidze at gmail.com>
Date:   Mon Jul 4 21:01:12 2011 +0200

    Move the munzip function in the Zip type class;

>---------------------------------------------------------------

 Control/Monad/Zip.hs |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/Control/Monad/Zip.hs b/Control/Monad/Zip.hs
index 8c431bd..9d71a53 100644
--- a/Control/Monad/Zip.hs
+++ b/Control/Monad/Zip.hs
@@ -3,6 +3,7 @@
 -- |
 -- Module      :  Control.Monad.Zip
 -- Copyright   :  (c) Nils Schweinsberg 2011,
+--                (c) George Giorgidze 2011
 --                (c) University Tuebingen 2011
 -- License     :  BSD-style (see the file libraries/base/LICENSE)
 -- Maintainer  :  libraries at haskell.org
@@ -40,8 +41,13 @@ class Monad m => MonadZip m where
     mzipWith :: (a -> b -> c) -> m a -> m b -> m c
     mzipWith f ma mb = liftM (uncurry f) (mzip ma mb)
 
-instance MonadZip [] where
-    mzip = zip
+    munzip :: m (a,b) -> (m a, m b)
+    munzip mab = (liftM fst mab, liftM snd mab)
+    -- munzip is a member of the class because sometimes
+    -- you can implement it more efficiently than the
+    -- above default code.  See Trac #4370 comment by giorgidze
 
-munzip :: MonadZip m => m (a,b) -> (m a, m b)
-munzip mab = (liftM fst mab, liftM snd mab)
+instance MonadZip [] where
+    mzip     = zip
+    mzipWith = zipWith
+    munzip   = unzip
\ No newline at end of file