$var(idx) = 0;
    while ($(cgrret(AttributesDigest){s.select,$var(idx),,}) != NULL) {
        $avp($(cgrret(AttributesDigest){s.select,$var(idx),,}{s.select,0,:}))
            = $(cgrret(AttributesDigest){s.select,$var(idx),,}{s.select,1,:});
        $var(idx) = $var(idx) + 1;
    }