Might not be exactly what you're looking for, but Control.Arrow has a rich set of operators that can be used to combine functions.

For instance, there's an example on http://en.wikibooks.org/wiki/Haskell/Understanding_arrows showing an addA function that can be used to apply two functions to the same argument and add the results:

Prelude> import Control.Arrow
Prelude Control.Arrow> let addA f g = f &&& g >>> arr (\ (y, z) -> y + z)
Prelude Control.Arrow> addA (+2) (*5) 10
62

If you're set on using the + and * operators, I'm guessing it's not possible to define a (sane) instance of Num for (->), but it would probably be instructive to try.

On Sat, Aug 31, 2013 at 10:01 PM, Christopher Howard <christopher.howard@frigidcode.com> wrote:

Hi. I was just curious about something. In one of my math textbooks I see expressions like this

f + g

or

(f + g)(a)

where f and g are functions. What is meant is

f(a) + g(a)

Is there a way in Haskell you can make use of syntax like that (i.e., expressions like f + g and f * g to create a new function), perhaps by loading a module or something?

_______________________________________________
Haskell-Cafe mailing list
Haskell-Cafe@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-cafe