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

Stephen Tetley schrieb:

Christian Maeder wrote:

...

Hoogle did not find a function of type:

(b -> b -> b) -> (a -> b) -> (a -> b) -> a -> b

or (b -> c -> d) -> (a -> b) -> (a -> c) -> a -> d

But maybe such a function is worth being added to Data.Function.

I did not find liftM2 (or liftA2) although I "knew" liftM2 and instance Functor/Monad ((->) a).

Hello Christian

This is the big Phi or S' combinator. I would certainly second its addition to Data.Function.

sprime p q r s = p (q s) (r s)

At least for documentation purposes (other than this thread) such an explicit definition makes sense to be put into a source. Be it just to show the (non-)obvious. Cheers Christian Btw. for the actual problem I suggest now: ((< 0.5) . abs)