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Added two more helper functions to the Utils module

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Neil Brown 2007-11-09 11:19:09 +00:00
parent 47f5e36f9c
commit af1574643d
1 changed files with 12 additions and 0 deletions
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12
common/Utils.hs
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@ -115,6 +115,12 @@ transformPair f g (x,y) = (f x, g y)
foldFuncs :: [a -> a] -> a -> a foldFuncs :: [a -> a] -> a -> a
foldFuncs = foldl (.) id foldFuncs = foldl (.) id
-- | Folds a list of monadic modifier functions into a single function
foldFuncsM :: Monad m => [a -> m a] -> a -> m a
foldFuncsM = foldl chain return
where
chain f0 f1 x = f0 x >>= f1
-- | Like the reflection of map. Instead of one function and multiple data, -- | Like the reflection of map. Instead of one function and multiple data,
-- we have multiple functions and one data. -- we have multiple functions and one data.
applyAll :: a -> [a -> b] -> [b] applyAll :: a -> [a -> b] -> [b]
@ -129,3 +135,9 @@ seqPair :: Monad m => (m a, m b) -> m (a,b)
seqPair (x,y) = do x' <- x seqPair (x,y) = do x' <- x
y' <- y y' <- y
return (x',y') return (x',y')
-- | Forms the powerset of a given list.
-- It uses the list monad cleverly, and it scares me. But it works.
-- Taken from: http://www.haskell.org/haskellwiki/Blow_your_mind
powerset :: [a] -> [[a]]
powerset = filterM (const [True, False])