Question

Is is possible to have reference to module in haskell? I have several modules, each of them expose the same interface(two functions of same name and signature). Is it possible to have a list of such modules, to call function for each module.

Answer 1

What about defining a data type for the interface? Each module provides a single instance of the datatype and then you can iterate through all instances.

-- ModuleInterface.hs
-- Replace types of the functions with actual types
data ModuleInterface = ModuleInterface (Int -> Bool -> Int) (String -> Int)

-- ModuleA.hs
moduleInterface :: ModuleInterface
moduleInterface = ModuleInterface f1 f2
-- Declare f1 and f2

-- ModuleB.hs
moduleInterface :: ModuleInterface
moduleInterface = ModuleInterface f1 f2
-- Declare f1 and f2

-- Main.hs
-- Simple example showing how to "call" all of the functions. If you are doing
-- IO, then you would have to use something like mapM.
transform :: [ModuleInterface] -> Int -> Bool -> String -> [(Int, Int)]
transform interfaces i b s = map f interfaces
    where f (ModuleInterface g h) = (g i b, h s)