Re: [Haskell-beginners] \x -> x < 0.5 && x > -0.5

Am Freitag 23 Oktober 2009 16:25:57 schrieb pl:

filter ((<=0.5) . abs) xs

Would be filter ((< 0.5) . abs). Yes, it's fine. However, if the range is not symmetrical about 0, this is not so nice anymore: cap lo hi = filter (\x -> lo < x && x < hi) cap lo hi = filter (liftM2 (&&) (lo <) (< hi)) cap lo hi = filter ((&&) <$> (lo <) <*> (< hi)) cap lo hi = filter ((< halflength) . abs . subtract mid) where mid = (lo+hi)/2 halflength = (hi-lo)/2

On Mon, Oct 19, 2009 at 10:49 AM, Michael Mossey wrote:

...

Is there a nifty way to write

filter (\x -> x < 0.5 && x > -0.5) xs

without explicitly using x?

Maybe arrows? I have a vague understanding that arrows can "send" an argument to more than one computation.

-Mike