haskell tuple nth functions

gistfile1.hs

{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE FlexibleInstances #-}
class First a b | b -> a where
    first' :: b -> a

class Second a b | b -> a where
    second' :: b -> a

instance First a ((,) a b) where
    first' (x,_) = x

instance First a ((,,) a b c) where
    first' (x,_,_) = x

instance Second b ((,) a b) where
    second' (_,y) = y

instance Second b ((,,) a b c) where
    second' (_,y,_) = y