adamc@841: datatype t = datatype Basis.option
adamc@841: 
adamc@841: fun isSome [a] x =
adamc@841:     case x of
adamc@841:         None => False
adamc@841:       | Some _ => True
adamc@844: 
adamc@844: fun mp [a] [b] f x =
adamc@844:     case x of
adamc@844:         None => None
adamc@844:       | Some y => Some (f y)