28 May
2013
28 May
'13
5:11 a.m.
On Tue, May 28, 2013 at 10:54 AM, Dominique Devriese < dominique.devriese@cs.kuleuven.be> wrote:
Hi all,
I often find myself needing the following definitions:
mapPair :: (a -> b) -> (c -> d) -> (a,c) -> (b,d) mapPair f g (x,y) = (f x, g y)
That's Control.Arrow.(***), e.g.: ghci> (+3) *** (*5) $ (20,30) (23,150)
mapFst :: (a -> b) -> (a,c) -> (b,c) mapFst f = mapPair f id
mapSnd :: (b -> c) -> (a,b) -> (a,c) mapSnd = mapPair id
That's Control.Arrow.{first, second}:
ghci> first (+10) (1,1)
(11,1)
ghci> second (+10) (1,1)
(1,11)
G
--
Gregory Collins