{-# LANGUAGE CPP #-}
{-# LANGUAGE GADTs #-}
{-# LANGUAGE Rank2Types #-}
{-# LANGUAGE TypeFamilies #-}
#if __GLASGOW_HASKELL__ >= 706
{-# LANGUAGE PolyKinds #-}
#endif
module Control.Lens.Equality
(
Equality, Equality'
, AnEquality, AnEquality'
, runEq
, substEq
, mapEq
, fromEq
, simply
, simple
, Identical(..)
) where
import Control.Lens.Type
import Data.Proxy (Proxy)
#ifdef HLINT
{-# ANN module "HLint: ignore Use id" #-}
{-# ANN module "HLint: ignore Eta reduce" #-}
#endif
data Identical a b s t where
Identical :: Identical a b a b
#if __GLASGOW_HASKELL__ >= 706
type AnEquality (s :: k1) (t :: k2) (a :: k1) (b :: k2) = Identical a (Proxy b) a (Proxy b) -> Identical a (Proxy b) s (Proxy t)
#else
type AnEquality s t a b = Identical a (Proxy b) a (Proxy b) -> Identical a (Proxy b) s (Proxy t)
#endif
type AnEquality' s a = AnEquality s s a a
runEq :: AnEquality s t a b -> Identical s t a b
runEq l = case l Identical of Identical -> Identical
{-# INLINE runEq #-}
substEq :: AnEquality s t a b -> ((s ~ a, t ~ b) => r) -> r
substEq l = case runEq l of
Identical -> \r -> r
{-# INLINE substEq #-}
#if __GLASGOW_HASKELL__ >= 706
mapEq :: forall (s :: k1) (t :: k2) (a :: k1) (b :: k2) (f :: k1 -> *) . AnEquality s t a b -> f s -> f a
#else
mapEq :: AnEquality s t a b -> f s -> f a
#endif
mapEq l r = substEq l r
{-# INLINE mapEq #-}
fromEq :: AnEquality s t a b -> Equality b a t s
fromEq l = substEq l id
{-# INLINE fromEq #-}
simply :: (Optic' p f s a -> r) -> Optic' p f s a -> r
simply = id
{-# INLINE simply #-}
simple :: Equality' a a
simple = id
{-# INLINE simple #-}