{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE NoImplicitPrelude #-}
{-# OPTIONS_GHC -Wno-inline-rule-shadowing #-}
    -- The RULES for the methods of class Arrow may never fire
    -- e.g. compose/arr;  see Trac #10528

-----------------------------------------------------------------------------
-- |
-- Module      :  Control.Arrow
-- Copyright   :  (c) Ross Paterson 2002
-- License     :  BSD-style (see the LICENSE file in the distribution)
--
-- Maintainer  :  libraries@haskell.org
-- Stability   :  provisional
-- Portability :  portable
--
-- Basic arrow definitions, based on
--
--  * /Generalising Monads to Arrows/, by John Hughes,
--    /Science of Computer Programming/ 37, pp67-111, May 2000.
--
-- plus a couple of definitions ('returnA' and 'loop') from
--
--  * /A New Notation for Arrows/, by Ross Paterson, in /ICFP 2001/,
--    Firenze, Italy, pp229-240.
--
-- These papers and more information on arrows can be found at
-- <http://www.haskell.org/arrows/>.

module Control.Arrow (
    -- * Arrows
    Arrow(..), Kleisli(..),
    -- ** Derived combinators
    returnA,
    (^>>), (>>^),
    (>>>), (<<<), -- reexported
    -- ** Right-to-left variants
    (<<^), (^<<),
    -- * Monoid operations
    ArrowZero(..), ArrowPlus(..),
    -- * Conditionals
    ArrowChoice(..),
    -- * Arrow application
    ArrowApply(..), ArrowMonad(..), leftApp,
    -- * Feedback
    ArrowLoop(..)
    ) where

import Data.Tuple ( fst, snd, uncurry )
import Data.Either
import Control.Monad.Fix
import Control.Category
import GHC.Base hiding ( (.), id )

infixr 5 <+>
infixr 3 ***
infixr 3 &&&
infixr 2 +++
infixr 2 |||
infixr 1 ^>>, >>^
infixr 1 ^<<, <<^

-- | The basic arrow class.
--
-- Instances should satisfy the following laws:
--
--  * @'arr' id = 'id'@
--
--  * @'arr' (f >>> g) = 'arr' f >>> 'arr' g@
--
--  * @'first' ('arr' f) = 'arr' ('first' f)@
--
--  * @'first' (f >>> g) = 'first' f >>> 'first' g@
--
--  * @'first' f >>> 'arr' 'fst' = 'arr' 'fst' >>>