Applicative.hs

{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE PolymorphicComponents #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FunctionalDependencies #-}
-- .$Header: c:/Source/Haskell/Wrapper/Data/Flex/RCS/Applicative.hs,v 1.3 2011/09/20 23:35:55 dosuser Exp dosuser $
module Data.Flex.Applicative (
    -- * Common flexible Applicative instance selection types and classes
    -- ** Analysis class for @'Applicative'@ instance selection
    FWApplicative,
    -- ** Instance selectors
    FWDefaultApplicative(..),
    -- ** Function identifier types for @'Apply'@
    FWPure(..),
    FWCombine(..),
    -- ** Polymorphic function wrappers
    WrapPure(..),
    WrapCombine(..)
) where

-- | Analysis class for @'Applicative'@ instance selection
-- You need a specific instance of this for any instance selectors
-- you may define.
class FWApplicative (f :: * -> *) r | f -> r

-- | Instance selector type for the default @'Applicative'@
-- instances
data FWDefaultApplicative = FWDefaultApplicative

-- | Function identifier type for @'Apply'@.
-- You need a corresponding instance of @'Apply'@ for any
-- instance selectors you may define.
data FWPure t (f :: * -> *) = FWPure

-- | Polymorphic function wrapper for @'pure'@
newtype WrapPure f = WrapPure {unwrapPure :: forall a. a -> f a}

-- | Function identifier type for @'Apply'@.
-- You need a corresponding instance of @'Apply'@ for any
-- instance selectors you may define.
data FWCombine t (f :: * -> *) = FWCombine

-- | Polymorphic function wrapper for @'<*>'@
newtype WrapCombine f =
    WrapCombine {unwrapCombine :: forall a b. f (a -> b) -> (f a -> f b)}

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