ref: 15a4c1e063cbd875ee6582e89671e5a79377b7a4
dir: /lib/Control/Alternative.hs/
module Control.Alternative(module Control.Alternative) where
import Primitives
import Control.Applicative
import Data.Bool_Type
import Data.Functor
import Data.List_Type
infixl 3 <|>
class Applicative f => Alternative f where
empty :: forall a . f a
(<|>) :: forall a . f a -> f a -> f a
some :: forall a . f a -> f [a]
some a = (:) <$> a <*> many a
many :: forall a . f a -> f [a]
many a = some a <|> pure []
guard :: forall f a . Alternative f => Bool -> f ()
guard b = if b then pure () else empty
asum :: forall f a . Alternative f => [f a] -> f a
asum [] = empty
asum (a:as) = a <|> asum as