function verifyRingHasNoSubRing(Ring ring)
        internal
        constant
    {
        uint ringSize = ring.orders.length;
        
        for (uint i = 0; i < ringSize - 1; i++) {
            address tokenS = ring.orders[i].order.tokenS;
            for (uint j = i + 1; j < ringSize; j++) {
                ErrorLib.check(
                    tokenS != ring.orders[j].order.tokenS,
                    "found sub-ring"
                );
            }
        }
    }