ard_equal: standard_is_equal (other)
        end

    frozen clone (other: detachable ANY): like other
            -- Void if `other' is void; otherwise new object
            -- equal to `other'
            --
            -- For non-void `other', `clone' calls `copy';
            -- to change copying/cloning semantics, redefine `copy'.
        obsolete
            "Use `twin' instead."
        do
            if other /= Void then
                Result := other.twin
            end
        e