DeriveDataTypeable, GeneralizedNewtypeDeriving,
FlexibleInstances, StandaloneDeriving,
PatternGuards, EmptyDataDecls, NoImplicitPrelude
DeriveDataTypeable, GeneralizedNewtypeDeriving,
FlexibleInstances, StandaloneDeriving,
PatternGuards, EmptyDataDecls, NoImplicitPrelude