Wolfram wrote: | > | > Control.Combinators? Such general beasts as mapFst, mapSnd | > and >< from Data.Graph.Inductive.Query.Monad could go in | > there, as could other pair handling combinators like (f <&> | > g) x = (f x, g x) | | Pair handling combinators could go into Data.Tuple. Many of those combinators can be expressed conveniently using functions from Control.Arrow. | > swap (x,y) = (y,x)
swap = flip (,) :p
| > pupd f g (x,y) = (f x, g y)
pupd = (***)
| > mapPair f (x,y) = (f x, f y)
mapPair = join (***)
| > mapTriple f (x,y,z) = (f x, f y, f z) Not this one. I sometimes use nested pairs instead of triples to allow use of the basic arrow combinators. | > pupd1 f (x,y) = (f x, y)
pupd1 = first
| > pupd2 g (x,y) = (x, g y)
pupd2 = second
| > keep1 f p@(x,y) = (x, f p)
keep1 = (fst &&&)
| > keep2 f p@(x,y) = (f p, y)
keep2 = (&&& snd)
I'm not opposing introduction of these special tuple combinators, but it may be good to reuse existing code. Regards, Arie