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

[Christian Maeder]

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)