Applicative.hs

{-# LANGUAGE CPP  #-}
{-# LANGUAGE Safe #-}

{- |
Copyright:  (c) 2016 Stephen Diehl
            (c) 2016-2018 Serokell
            (c) 2018-2020 Kowainik
SPDX-License-Identifier: MIT
Maintainer:  Kowainik <xrom.xkov@gmail.com>
Stability:   Stable
Portability: Portable

This module contains reexports of 'Applicative' and related functional.
Additionally, it provides convenient combinators to work with 'Applicative'.
-}

module Relude.Applicative
    ( -- * Reexports
      -- $reexports
      Alternative (..)
    , Applicative (..)
    , Const (..)
    , ZipList (..)
#if __GLASGOW_HASKELL__ < 802
    , liftA2
#endif
    , liftA3
    , optional
    , (<**>)

      -- * Combinators
    , pass
    , appliedTo
    ) where

import Control.Applicative (Alternative (..), Applicative (..), Const (..), ZipList (..), liftA2,
                            liftA3, optional, (<**>))


-- $setup
-- >>> import Relude
-- >>> import Relude.Monad (Maybe)

-- | Shorter alias for @pure ()@.
--
-- >>> pass :: Maybe ()
-- Just ()
pass :: Applicative f => f ()
pass = pure ()
{-# INLINE pass #-}

{- | Named version of the '<**>' operator, which is '<*>' but flipped. For
chaining applicative operations in forward applications using
'Relude.Function.&'.

>>> Just (+ 1) & appliedTo (Just 2)
Just 3
>>> Just (+) & appliedTo (Just 1) & appliedTo (Just 2)
Just 3
>>> Nothing & appliedTo (Just 2)
Nothing

@since 0.5.0
-}
appliedTo :: Applicative f => f a -> f (a -> b) -> f b
appliedTo = (<**>)
{-# INLINE appliedTo #-}

{- $reexports
Main data types and functions reexported from "Control.Applicative".
-}