continuational

    enum Option<T> {
        None,
        Some(T),
    }

  fn Maybe(comptime T: type) type {
    return union(enum) {
        value: T,
        nothing,

        const Self = @This();

        pub fn just(the_val: T) Self   { return .{ .value = the_val }; }
        pub fn nothing() Self          { return .nothing; }

      }
    }

    data Maybe a = Just a | Nothing