Overloaded Strings Example

OverloadedStrings.hs

{-# LANGUAGE OverloadedStrings #-}

import GHC.Exts ( IsString(..) )

data Foo = A | B | Other String deriving Show

instance IsString Foo where
  fromString "A" = A
  fromString "B" = B
  fromString xs  = Other xs

tests :: [ Foo ]
tests =  [ "A", "B", "Testing" ]

main :: IO ()
main = mapM_ print tests

Thank you for the example, simple and self-explanatory.