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|
-----------------------------------------------------------------------------
-- |
-- Module : Data.Strict.Tuple
-- Copyright : (c) 2006-2007 Roman Leshchinskiy
-- License : BSD-style (see the file LICENSE)
--
-- Maintainer : Roman Leshchinskiy <rl@cse.unsw.edu.au>
-- Stability : experimental
-- Portability : portable
--
-- Strict pairs.
--
-- Same as regular Haskell pairs, but @(x :*: _|_) = (_|_ :*: y) = _|_@
--
-----------------------------------------------------------------------------
{-# OPTIONS_GHC -fglasgow-exts #-}
module Data.Strict.Tuple (
Pair(..)
#ifndef __HADDOCK__
#ifdef __GLASGOW_HASKELL__
, (:!:)
#endif
#endif
, fst
, snd
, curry
, uncurry
) where
import Prelude hiding( fst, snd, curry, uncurry )
import Data.Array (Ix)
infixl 2 :!:
-- | The type of strict pairs.
data Pair a b = !a :!: !b deriving(Eq, Ord, Show, Read, Bounded, Ix)
#ifndef __HADDOCK__
#ifdef __GLASGOW_HASKELL__
-- This gives a nicer syntax for the type but only works in GHC for now.
type (:!:) = Pair
#endif
#endif
-- | Extract the first component of a strict pair.
fst :: Pair a b -> a
fst (x :!: _) = x
-- | Extract the second component of a strict pair.
snd :: Pair a b -> b
snd (_ :!: y) = y
-- | Curry a function on strict pairs.
curry :: (Pair a b -> c) -> a -> b -> c
curry f x y = f (x :!: y)
-- | Convert a curried function to a function on strict pairs.
uncurry :: (a -> b -> c) -> Pair a b -> c
uncurry f (x :!: y) = f x y
|
