if (x) {
        x0 = z[0], x1 = z[1];
        if (y) x0 = x0[0], x1 = x1[0];
        extentDomain[0][0] = x0, extentDomain[1][0] = x1;
        if (x.invert) x0 = x(x0), x1 = x(x1);