def identity_monad():
return monad(identity_functor, identity, identity)
def error_monad():
return monad(error_functor, join, unit)
def list_monad():
return monad(list_functor, join, unit)
def none_monad():
return monad(none_functor, join, unit)
def maybe_monad():
return monad(maybe_functor, join, unit)