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|
{- monadic conditional operators
-
- Copyright 2011 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Utility.Conditional where
import Control.Monad (when, unless)
untilTrue :: Monad m => [v] -> (v -> m Bool) -> m Bool
untilTrue [] _ = return False
untilTrue (v:vs) a = do
ok <- a v
if ok then return ok else untilTrue vs a
whenM :: Monad m => m Bool -> m () -> m ()
whenM c a = c >>= flip when a
unlessM :: Monad m => m Bool -> m () -> m ()
unlessM c a = c >>= flip unless a
(>>?) :: Monad m => m Bool -> m () -> m ()
(>>?) = whenM
(>>!) :: Monad m => m Bool -> m () -> m ()
(>>!) = unlessM
-- low fixity allows eg, foo bar >>! error $ "failed " ++ meep
infixr 0 >>?
infixr 0 >>!
|
