PostTagSystem implements a tag system introduced by Emil Post in 1921:
{{0, _, _} -> {0, 0}, {1, _, _} -> {1, 1, 0, 1}}The interesting feature of this system is that it appears to always reach a fixed point, however it does that in a number of generations that varies widely with initial state of queue.
This repository implements the evolution of that system in an attempt to prove that it always reaches a fixed point.