Question

I’ve got a name clash between two different Haskell modules that want to use the same infix operator (<*>). The Haskell 98 report says that

modid.varsym 

is permitted, but I can’t get it to work. In their entirety here are Test.hs:

module Test where  import qualified Test2 as T  three = T.<*> 

and Test2.hs:

module Test2 where (<*>) = 3 

But trying to compile results in an error message:

Test.hs:6:12: parse error on input `T.<*>' 

I tried T.(<*>) but that doesn’t work either.

How can I refer to a symbolic name defined in a module imported by import qualified?

Answer 1

try

three = (T.<*>) 

It’s weird to define an infix operator as an integer. Let’s consider \\ (the set difference operator):

import qualified Data.List as L  foo = [1..5] L.\\ [1..3] -- evaluates to [4,5] diff = (L.\\) 

As you can see above, L.\\ is a qualified infix operator; and it still works as an infix operator. To use it as a value, you put parentheses around the whole thing.