Overload

This library provides a mechanism for overloading an indentifier with mutliple definitions. The number of overloads is finite and have to be defined at once.

The advantage of this library over the regular typeclass approach is that it behaves very well with type inference.

  {-# LANGUAGE TemplateHaskell, TypeFamilies, FlexibleInstances #-}
  module Overload.Example where

  import Data.Maybe
  import Overload

  f1 :: Bool
  f1 = True

  f2 :: Int -> Int
  f2 x = x + 1

  f3 :: Num a = Maybe a
  f3 = Just 0

  overload "f" ['f1, 'f2, 'f3]

  test :: IO ()
  test = do
      print (f 1)
      print (f && True)
      print (fromMaybe 10 f)

Notice that we didn't have to annotate anything. For the function case it was enough to use f as a function. Since there's only one overload that's a function, the argument and the return value are inferred as Ints.

Documentation

overload :: String -> [Name] -> Q [Dec]

Generates a new function with the given name that can behave like multiple functions.