Am Dienstag, 11. November 2008 12:40 schrieb Bas van Gijzel:
Hi,
I'm trying to understand pointfree style better, but it's not coming along as well as I'd like it to. The thing I can't get to work is to reduce an argument that is used more than once in a function.
My function looks like this now (which works like it should): f x = g ((h . i) x) x
But I'd like to reduce the last argument x. I've looked at the wiki[1] but I couldn't find a systematic way to obtain pointfree functions when they get more complicated. Any pointers to pages or papers with more examples of obtaining pointfree functions are appreciated.
lambdabot can pointfree your functions, the command is @pl: lambdabot> @pl \x -> \y -> (y,x) flip (,) lambdabot> @pl \x -> g ((h . i) x) x g =<< h . i (the monad here is ((->) a), where x :: a, I think, you need Control.Monad.Instances for that to be in scope). I'm not sure reading lambdabot's sources is a good way to learn how to systematically pointfree functions, but looking at lambdabot's results should help.
Thanks,
Bas van Gijzel
Cheers, Daniel