Functor.hs

{-# LANGUAGE ScopedTypeVariables, PolymorphicComponents #-}
{-# LANGUAGE MultiParamTypeClasses, FunctionalDependencies #-}
-- .$Header: c:/Source/Haskell/Wrapper/Data/Flex/RCS/Functor.hs,v 1.4 2011/09/20 23:36:59 dosuser Exp dosuser $
module Data.Flex.Functor (
    -- * Common flexible Functor instance selection types and classes
    -- ** Analysis class for @'Functor'@ instance selection
    FWFunctor,
    -- ** Instance selector
    FWDefaultFunctor(..),
    -- ** Function identifier type for @'Apply'@
    FWFmap(..),
    -- ** Polymorphic function wrapper
    WrapFmap(..)
) where

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

-- | Instance selector type for the default @'Functor'@
-- instances
data FWDefaultFunctor = FWDefaultFunctor

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

-- | Polymorphic function wrapper for @'fmap'@
newtype WrapFmap f =
    WrapFmap {unwrapFmap :: forall a b. (a -> b) -> (f a -> f b)}

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