65 lines
1.6 KiB
Haskell
65 lines
1.6 KiB
Haskell
{-# LANGUAGE Safe #-}
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{-# LANGUAGE NoImplicitPrelude #-}
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module Protolude.Bool (
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whenM
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, unlessM
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, ifM
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, guardM
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, bool
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, (&&^)
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, (||^)
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, (<&&>)
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, (<||>)
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) where
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import Data.Bool (Bool(..), (&&), (||))
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import Data.Function (flip)
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import Control.Applicative(Applicative, liftA2)
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import Control.Monad (Monad, MonadPlus, return, when, unless, guard, (>>=), (=<<))
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bool :: a -> a -> Bool -> a
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bool f t p = if p then t else f
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whenM :: Monad m => m Bool -> m () -> m ()
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whenM p m =
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p >>= flip when m
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unlessM :: Monad m => m Bool -> m () -> m ()
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unlessM p m =
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p >>= flip unless m
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ifM :: Monad m => m Bool -> m a -> m a -> m a
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ifM p x y = p >>= \b -> if b then x else y
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guardM :: MonadPlus m => m Bool -> m ()
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guardM f = guard =<< f
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-- | The '||' operator lifted to a monad. If the first
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-- argument evaluates to 'True' the second argument will not
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-- be evaluated.
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infixr 2 ||^ -- same as (||)
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(||^) :: Monad m => m Bool -> m Bool -> m Bool
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(||^) a b = ifM a (return True) b
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infixr 2 <||>
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-- | '||' lifted to an Applicative.
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-- Unlike '||^' the operator is __not__ short-circuiting.
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(<||>) :: Applicative a => a Bool -> a Bool -> a Bool
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(<||>) = liftA2 (||)
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{-# INLINE (<||>) #-}
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-- | The '&&' operator lifted to a monad. If the first
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-- argument evaluates to 'False' the second argument will not
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-- be evaluated.
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infixr 3 &&^ -- same as (&&)
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(&&^) :: Monad m => m Bool -> m Bool -> m Bool
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(&&^) a b = ifM a b (return False)
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infixr 3 <&&>
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-- | '&&' lifted to an Applicative.
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-- Unlike '&&^' the operator is __not__ short-circuiting.
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(<&&>) :: Applicative a => a Bool -> a Bool -> a Bool
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(<&&>) = liftA2 (&&)
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{-# INLINE (<&&>) #-}
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