Bifunctor.hs

{-# LANGUAGE Safe #-}

{- |
Module                  : Relude.Extra.Bifunctor
Copyright               : (c) 2018-2023 Kowainik
SPDX-License-Identifier : MIT
Maintainer              : Kowainik <xrom.xkov@gmail.com>
Stability               : Stable
Portability             : Portable

Useful combinators for bifunctors inside functors. This set of functions is
useful when you want to work with types like these ones:

@
foo :: IO (Either a b)
bar :: IO (a, b)

baz :: Maybe (Either a b)
qux :: Maybe (a, b)

doo :: (a, a)
dee :: Either a a
@

@since 0.1.0
-}

module Relude.Extra.Bifunctor
    ( bimapBoth
    , bimapF
    , firstF
    , secondF
    ) where

import Relude

{- | Maps a function over both elements of a bifunctor.

>>> bimapBoth length ([True], [False, True])
(1,2)
>>> map (bimapBoth not) [Left True, Right False]
[Left False,Right True]

@since 0.6.0.0
-}
bimapBoth :: Bifunctor f => (a -> b) -> f a a -> f b b
bimapBoth f = bimap f f
{-# INLINE bimapBoth #-}

{- | Fmaps functions for nested bifunctor. Short for @fmap (bimap f g)@.

>>> bimapF not length $ Just (False, ['a', 'b'])
Just (True,2)

@since 0.1.0
-}
bimapF  :: (Functor f, Bifunctor p) => (a -> c) -> (b -> d) -> f (p a b) -> f (p c d)
bimapF f g = fmap (bimap f g)
{-# INLINE bimapF #-}

{- | Short for @fmap . first@.

>>> firstF not $ Just (False, ['a', 'b'])
Just (True,"ab")

@since 0.1.0
-}
firstF  :: (Functor f, Bifunctor p) => (a -> c) -> f (p a b) -> f (p c b)
firstF = fmap . first
{-# INLINE firstF #-}

{- | Short for @fmap . second@.

>>> secondF length  $ Just (False, ['a', 'b'])
Just (False,2)

@since 0.1.0
-}
secondF  :: (Functor f, Bifunctor p) => (b -> d) -> f (p a b) -> f (p a d)
secondF = fmap . second
{-# INLINE secondF #-}