Prism.hs

{-# LANGUAGE ScopedTypeVariables #-}
-----------------------------------------------------------------------------
-- |
-- Module      :  Control.Lens.Internal.Prism
-- Copyright   :  (C) 2012-2016 Edward Kmett
-- License     :  BSD-style (see the file LICENSE)
-- Maintainer  :  Edward Kmett <ekmett@gmail.com>
-- Stability   :  experimental
-- Portability :  non-portable
--
----------------------------------------------------------------------------
module Control.Lens.Internal.Prism
  ( Market(..)
  , Market'
  ) where

import Prelude ()

import Control.Lens.Internal.Prelude

------------------------------------------------------------------------------
-- Prism: Market
------------------------------------------------------------------------------

-- | This type is used internally by the 'Control.Lens.Prism.Prism' code to
-- provide efficient access to the two parts of a 'Prism'.
data Market a b s t = Market (b -> t) (s -> Either t a)

-- | @type 'Market'' a s t = 'Market' a a s t@
type Market' a = Market a a

instance Functor (Market a b s) where
  fmap f (Market bt seta) = Market (f . bt) (either (Left . f) Right . seta)
  {-# INLINE fmap #-}

instance Profunctor (Market a b) where
  dimap f g (Market bt seta) = Market (g . bt) (either (Left . g) Right . seta . f)
  {-# INLINE dimap #-}
  lmap f (Market bt seta) = Market bt (seta . f)
  {-# INLINE lmap #-}
  rmap f (Market bt seta) = Market (f . bt) (either (Left . f) Right . seta)
  {-# INLINE rmap #-}

  (#.) _ = coerce
  {-# INLINE (#.) #-}
  (.#) p _ = coerce p
  {-# INLINE (.#) #-}

instance Choice (Market a b) where
  left' (Market bt seta) = Market (Left . bt) $ \sc -> case sc of
    Left s -> case seta s of
      Left t -> Left (Left t)
      Right a -> Right a
    Right c -> Left (Right c)
  {-# INLINE left' #-}
  right' (Market bt seta) = Market (Right . bt) $ \cs -> case cs of
    Left c -> Left (Left c)
    Right s -> case seta s of
      Left t -> Left (Right t)
      Right a -> Right a
  {-# INLINE right' #-}