{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE NoImplicitPrelude #-}

-----------------------------------------------------------------------------
-- |
-- Module      :  Data.Tuple
-- Copyright   :  (c) The University of Glasgow 2001
-- License     :  BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer  :  libraries@haskell.org
-- Stability   :  experimental
-- Portability :  portable
--
-- Functions associated with the tuple data types.
--
-----------------------------------------------------------------------------

module Data.Tuple
  ( fst
  , snd
  , curry
  , uncurry
  , swap
  ) where

import GHC.Base ()      -- Note [Depend on GHC.Tuple]

default ()              -- Double isn't available yet

-- ---------------------------------------------------------------------------
-- Standard functions over tuples

-- | Extract the first component of a pair.
fst                     :: (a,b) -> a
fst :: (a, b) -> a
fst (a
x,b
_)               =  a
x

-- | Extract the second component of a pair.
snd                     :: (a,b) -> b
snd :: (a, b) -> b
snd (a
_,b
y)               =  b
y

-- | 'curry' converts an uncurried function to a curried function.
--
-- ==== __Examples__
--
-- >>> curry fst 1 2
-- 1
curry                   :: ((a, b) -> c) -> a -> b -> c
curry :: ((a, b) -> c) -> a -> b -> c
curry (a, b) -> c
f a
x b
y             =  (a, b) -> c
f (a
x, b
y)

-- | 'uncurry' converts a curried function to a function on pairs.
--
-- ==== __Examples__
--
-- >>> uncurry (+) (1,2)
-- 3
--
-- >>> uncurry ($) (show, 1)
-- "1"
--
-- >>> map (uncurry max) [(1,2), (3,4), (6,8)]
-- [2,4,8]
uncurry                 :: (a -> b -> c) -> ((a, b) -> c)
uncurry :: (a -> b -> c) -> (a, b) -> c
uncurry a -> b -> c
f (a, b)
p             =  a -> b -> c
f ((a, b) -> a
forall a b. (a, b) -> a
fst (a, b)
p) ((a, b) -> b
forall a b. (a, b) -> b
snd (a, b)
p)

-- | Swap the components of a pair.
swap                    :: (a,b) -> (b,a)
swap :: (a, b) -> (b, a)
swap (a
a,b
b)              = (b
b,a
a)

-- $setup
-- >>> import Prelude hiding (curry, uncurry, fst, snd)