datatype t = datatype Basis.option
fun eq [a] (_ : eq a) =
mkEq (fn x y =>
case (x, y) of
(None, None) => True
| (Some x, Some y) => x = y
| _ => False)
fun isSome [a] x =
case x of
None => False
| Some _ => True
fun mp [a] [b] f x =
case x of
None => None
| Some y => Some (f y)
fun bind [a] [b] f x =
case x of
None => None
| Some y => f y