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

[Brent Yorgey]

On Tue, Oct 20, 2009 at 04:29:43PM +0100, Stephen Tetley wrote:
> 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.
> 
> 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)

But this function already exists in the standard libraries: it is
called liftM2/liftA2, specialized to the ((->) e) monad/applicative
instance.  This is what the rest of the thread has been talking about.

-Brent