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Diffstat (limited to 'Utility/Monad.hs')
-rw-r--r-- | Utility/Monad.hs | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/Utility/Monad.hs b/Utility/Monad.hs new file mode 100644 index 000000000..9523e1716 --- /dev/null +++ b/Utility/Monad.hs @@ -0,0 +1,26 @@ +{- monadic stuff + - + - Copyright 2010-2011 Joey Hess <joey@kitenet.net> + - + - Licensed under the GNU GPL version 3 or higher. + -} + +module Utility.Monad where + +import Data.Maybe +import Control.Monad (liftM) + +{- Return the first value from a list, if any, satisfying the given + - predicate -} +firstM :: (Monad m) => (a -> m Bool) -> [a] -> m (Maybe a) +firstM _ [] = return Nothing +firstM p (x:xs) = do + q <- p x + if q + then return (Just x) + else firstM p xs + +{- Returns true if any value in the list satisfies the preducate, + - stopping once one is found. -} +anyM :: (Monad m) => (a -> m Bool) -> [a] -> m Bool +anyM p = liftM isJust . firstM p |