{-# LANGUAGE FunctionalDependencies #-}

module Main where

class Mult a b c | a b -> c where
    (.*) :: a -> b -> c

-- A quantity with units of a/b
newtype Frac a b = Frac {val :: Float}

instance Mult (Frac a b) (Frac b a) Float where
    (Frac x) .* (Frac y) = x*y
-- If a=d, this matches above instance, causing a conflict
instance Mult (Frac a x) (Frac x d) (Frac a d) where
    (Frac x) .* (Frac y) = Frac (x*y)


main :: IO ()
main = print "hello, world"