kyama

// 
// Zero-suppressed binary decision diagram with family algebra operations
//
// References: 
//   S. Minato (1993): 
//     Zero-suppressed BDDs for set manipulation in combinatorial problems.
//     Proceedings of the 30st annual Design Automation Conference, pp. 272-277.
//   S. Minato (1994):
//     Calculation of unate cube set algebra using zero-suppressed BDDs.
//     Proceedings of the 31st annual Design Automation Conference, pp. 420-424.