So I'm writing a program which returns a procedure for some given arithmetic problem, so I wanted to instance a couple of functions to Show so that I can print the same expression I evaluate when I test. The trouble is that the given code matches (-) to the first line when it should fall to the second.

{-# OPTIONS_GHC -XFlexibleInstances #-}

instance Show (t -> t-> t) where  
 show (+) = "plus"
 show (-) = "minus"  

main = print [(+),(-)]

returns

[plus,plus]

Am I just committing a motal sin printing functions in the first place or is there some way I can get it to match properly?

edit:I realise I am getting the following warning:

Warning: Pattern match(es) are overlapped
         In the definition of `show': show - = ...

I still don't know why it overlaps, or how to stop it.