{-# LANGUAGE FunctionalDependencies #-}

module Main where

-- | Something.
class Foo a b | a -> b

class Bar a b | a -> b, b -> a where bar :: a

-- | Something else.
class
  Baz a b c d
    | a b -> c d, -- Foo
      b c -> a d, -- Bar
      a c -> b d, -- Baz
      a c d -> b,
      a b d -> a b c d
  where
  baz :: a -> b