Example of overloading if-then-else in Haskell

RebindableIf.hs

{-# LANGUAGE RebindableSyntax #-}

import Prelude

data Height = Tall | Short

class IfThenElse b where
  ifThenElse :: b -> a -> a -> a

instance IfThenElse Bool where
  ifThenElse True  t _ = t
  ifThenElse False _ f = f

instance IfThenElse Height where
  ifThenElse Tall t _  = t
  ifThenElse Short _ f = f

main = do
  putStrLn $ if Tall then "A" else "B"
  putStrLn $ if False then "C" else "D"