FuzzyAddable.hs

{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FlexibleInstances #-}
import Prelude hiding ( (+) )
import qualified Prelude as P

class FuzzyAddable a b c where
    (+) :: a -> b -> c
instance FuzzyAddable String Int String where
    a + b = a ++ show b
instance Num a => FuzzyAddable a a a where
    a + b = a P.+ b

test1 :: String
test1 = "5" + (1 :: Int)
test2 :: Int
test2 = (5 :: Int) + (1 :: Int)