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author | Joey Hess <joey@kitenet.net> | 2012-03-17 00:22:05 -0400 |
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committer | Joey Hess <joey@kitenet.net> | 2012-03-17 00:38:40 -0400 |
commit | a362c46b70c45872ff8c479ba5a6716cf13cc8d8 (patch) | |
tree | e8f08204dc679a1d7c23b5cd466606e7877a2469 /Utility/Monad.hs | |
parent | d6624b6c798df401eb9e715810537d2b93935a76 (diff) |
fun with symbols
Nothing at all on hackage is using <&&> or <||>.
(Also, <&&> should short-circuit on failure.)
Diffstat (limited to 'Utility/Monad.hs')
-rw-r--r-- | Utility/Monad.hs | 16 |
1 files changed, 7 insertions, 9 deletions
diff --git a/Utility/Monad.hs b/Utility/Monad.hs index 5cc243290..9c85d31ca 100644 --- a/Utility/Monad.hs +++ b/Utility/Monad.hs @@ -8,7 +8,7 @@ module Utility.Monad where import Data.Maybe -import Control.Monad (liftM, liftM2) +import Control.Monad (liftM) {- Return the first value from a list, if any, satisfying the given - predicate -} @@ -31,15 +31,13 @@ ifM cond (thenclause, elseclause) = do c <- cond if c then thenclause else elseclause -{- monadic || - - - - Compare with (||) <$> ma <*> mb, which always runs both ma and mb. -} -orM :: Monad m => m Bool -> m Bool -> m Bool -orM ma mb = ifM ma ( return True , mb ) +{- short-circuiting monadic || -} +(<||>) :: Monad m => m Bool -> m Bool -> m Bool +ma <||> mb = ifM ma ( return True , mb ) -{- monadic && (for completeness) -} -andM :: Monad m => m Bool -> m Bool -> m Bool -andM = liftM2 (&&) +{- short-circuiting monadic && -} +(<&&>) :: Monad m => m Bool -> m Bool -> m Bool +ma <&&> mb = ifM ma ( mb , return False ) {- Runs an action, passing its value to an observer before returning it. -} observe :: Monad m => (a -> m b) -> m a -> m a |