[Haskell-beginners] \x -> x < 0.5 && x > -0.5
gtener at gmail.com
Mon Oct 19 05:05:20 EDT 2009
On Mon, Oct 19, 2009 at 10:49, Michael Mossey <mpm at alumni.caltech.edu> 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.
You can do that with arrows like this:
Prelude Control.Arrow> let rangeA x y = ((>x) &&& (<y)) >>> (uncurry (&&))
Prelude Control.Arrow> :t rangeA
rangeA :: (Ord a) => a -> a -> a -> Bool
Prelude Control.Arrow> filter (rangeA 4 8) [0..10]
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