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?
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