Rule integer

The rule integer of a given totalistic Life-like cellular automaton is a single integer expressing its birth and survival conditions.

The rule integer is computed by iterating over all B and S conditions, in order, writing down a one if a condition is present and a zero otherwise, and finally reversing the resulting string and interpreting it as a binary number. For instance, for Conway's Game of Life (B3/S23):

B0 B1 B2 B3 B4 B5 B6 B7 B8 S0 S1 S2 S3 S4 S5 S6 S7 S8

 0  0  0  1  0  0  0  0  0  0  0  1  1  0  0  0  0  0 = 000100000001100000

000100000001100000 => 000001100000001000b = 6152d

Rule integers are used by e.g. apgsearch 3.x (apgmera) to determine the circuitry needed to compute a given rule.

There is no generally accepted way of assigning rule integers or numbers to non-totalistic Life-like cellular automata.