Arrow.hs

{-# LANGUAGE CPP               #-}
{-# LANGUAGE FlexibleInstances #-}
-----------------------------------------------------------------------------------------
-- |
-- Module      :  FRP.Yampa.Arrow
-- Copyright   :  (c) Antony Courtney and Henrik Nilsson, Yale University, 2003
-- License     :  BSD-style (see the LICENSE file in the distribution)
--
-- Maintainer  :  ivan.perez@keera.co.uk
-- Stability   :  provisional
-- Portability :  portable
--
-- Arrow helper functions.
--
-----------------------------------------------------------------------------------------

module FRP.Yampa.Arrow (
    -- * Arrow plumbing aids
    dup,        -- :: a -> (a,a)

    -- * Liftings
    arr2,       -- :: Arrow a => (b->c->d) -> a (b,c) d
    arr3,       -- :: Arrow a => (b->c->d->e) -> a (b,c,d) e
    arr4,       -- :: Arrow a => (b->c->d->e->f) -> a (b,c,d,e) f
    arr5,       -- :: Arrow a => (b->c->d->e->f->g) -> a (b,c,d,e,f) g
) where

import Control.Arrow
#if __GLASGOW_HASKELL__ < 710
import Control.Applicative (Applicative(..))
#endif

-- * Arrow plumbing aids

-- | Duplicate an input.
dup :: a -> (a,a)
dup x = (x,x)

-- * Liftings

-- | Lift a binary function onto an arrow
arr2 :: Arrow a => (b -> c -> d) -> a (b, c) d
arr2 = arr . uncurry

-- | Lift a 3-ary function onto an arrow
arr3 :: Arrow a => (b -> c -> d -> e) -> a (b, c, d) e
arr3 = arr . \h (b, c, d) -> h b c d

-- | Lift a 4-ary function onto an arrow
arr4 :: Arrow a => (b -> c -> d -> e -> f) -> a (b, c, d, e) f
arr4 = arr . \h (b, c, d, e) -> h b c d e

-- | Lift a 5-ary function onto an arrow
arr5 :: Arrow a => (b -> c -> d -> e -> f -> g) -> a (b, c, d, e, f) g
arr5 = arr . \h (b, c, d, e, f) -> h b c d e f