[commit: Cabal] master: adding a lookup function for PSQs (4013b06)

[Ian Lynagh]

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

On branch  : master

http://hackage.haskell.org/trac/ghc/changeset/4013b0616e97ad81f0d93dda24cd402975015cc4

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

commit 4013b0616e97ad81f0d93dda24cd402975015cc4
Author: Andres Loeh <andres at well-typed.com>
Date:   Thu Oct 27 16:09:24 2011 +0000

    adding a lookup function for PSQs

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

 .../Distribution/Client/Dependency/Modular/PSQ.hs  |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/cabal-install/Distribution/Client/Dependency/Modular/PSQ.hs b/cabal-install/Distribution/Client/Dependency/Modular/PSQ.hs
index cc03189..e67c8dc 100644
--- a/cabal-install/Distribution/Client/Dependency/Modular/PSQ.hs
+++ b/cabal-install/Distribution/Client/Dependency/Modular/PSQ.hs
@@ -26,6 +26,9 @@ instance Foldable (PSQ k) where
 instance Traversable (PSQ k) where
   traverse f (PSQ xs) = PSQ <$> traverse (\ (k, v) -> (\ x -> (k, x)) <$> f v) xs
 
+lookup :: Eq k => k -> PSQ k v -> Maybe v
+lookup k (PSQ xs) = S.lookup k xs
+
 map :: (v1 -> v2) -> PSQ k v1 -> PSQ k v2
 map f (PSQ xs) = PSQ (fmap (\ (k, v) -> (k, f v)) xs)