I have them defined for my stuff.
Generally I find it much quicker to "roll my own" than to
(1) ask on this list if someone else has done it...
(2) look at arrows or
MyFavouriteCategoryTheoryBitOfFPBecauseICantGetAbstractEnough
and the try to figure out what is going on.
The joy of Haskell is both that rolling your own is often so easy,
and that there are lots of approaches out there that allow you to get abstract
as well...
Regards,
Andrew (Engineering graduate, feet still firmly embedded in concrete :-)
On 28 May 2013, at 09:54, Dominique Devriese 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)
>
> mapFst :: (a -> b) -> (a,c) -> (b,c)
> mapFst f = mapPair f id
>
> mapSnd :: (b -> c) -> (a,b) -> (a,c)
> mapSnd = mapPair id
>
> But they seem missing from the prelude and Hoogle or Hayoo only turn
> up versions of them in packages like scion or fgl. Has anyone else
> felt the need for these functions? Am I missing some generalisation
> of them perhaps?
>
> Regards,
> Dominique
>
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> Haskell-Cafe@haskell.org
> http://www.haskell.org/mailman/listinfo/haskell-cafe
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Director of Teaching and Learning - Undergraduate,
School of Computer Science and Statistics,
Room G.39, O'Reilly Institute, Trinity College, University of Dublin
http://www.scss.tcd.ie/Andrew.Butterfield/
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