From_monad.Monadinclude Preface_specs.Monad.WITH_RETURN with type 'a t := 'a tinclude Preface_specs.Monad.WITH_RETURN with type 'a t := 'a tinclude Preface_specs.Monad.WITH_RETURN with type 'a t := 'a tval return : 'a -> 'a tLift a value from 'a into a new 'a t.