Le pseudo-code:

      if (CMP (0, 1) > 0)
	SWAP (0 ,1);
      if (CMP (2, 3) > 0)
	SWAP (2, 3);
      if (CMP (0, 2) > 0) {
	SWAP (0, 2);
        SWAP (1, 3);
      }
      if (CMP (1, 2) <= 0)
        return;
      if (CMP (1, 3) > 0)
        ROLL (1, 2, 3);
      else
        SWAP (1, 2);