diff options
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 | |
parent | d6624b6c798df401eb9e715810537d2b93935a76 (diff) |
fun with symbols
Nothing at all on hackage is using <&&> or <||>.
(Also, <&&> should short-circuit on failure.)
Diffstat (limited to 'Utility')
-rw-r--r-- | Utility/Matcher.hs | 8 | ||||
-rw-r--r-- | Utility/Monad.hs | 16 |
2 files changed, 11 insertions, 13 deletions
diff --git a/Utility/Matcher.hs b/Utility/Matcher.hs index 71e1e17f4..9b6005767 100644 --- a/Utility/Matcher.hs +++ b/Utility/Matcher.hs @@ -78,8 +78,8 @@ match a m v = go m where go MAny = True go (MAnd m1 m2) = go m1 && go m2 - go (MOr m1 m2) = go m1 || go m2 - go (MNot m1) = not (go m1) + go (MOr m1 m2) = go m1 || go m2 + go (MNot m1) = not $ go m1 go (MOp o) = a o v {- Runs a monadic Matcher, where Operations are actions in the monad. -} @@ -87,8 +87,8 @@ matchM :: Monad m => Matcher (v -> m Bool) -> v -> m Bool matchM m v = go m where go MAny = return True - go (MAnd m1 m2) = andM (go m1) (go m2) - go (MOr m1 m2) = orM (go m1) (go m2) + go (MAnd m1 m2) = go m1 <&&> go m2 + go (MOr m1 m2) = go m1 <||> go m2 go (MNot m1) = liftM not (go m1) go (MOp o) = o v 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 |