Chapter 11: The Notion of Computation

Section 6: Emulating Cellular Automata with Other Systems

Mobile automata [emulating cellular automata]

Given the rules for an elementary cellular automaton in the form used on page 867, the following will construct a mobile automaton which emulates it:

vals = {x, p[0], q[0,0], q[0,1], q[1,0], q[1,1], p[1]}

CAToMA[rules_] := Table[(# -> Replace[#, {{q[a_,b_], p[c_], p[d_]} :> {q[c, {a,c,d}/.rules], 1}, {q[a_,b_], p[c_], x} :> {q[c, {a,c,0}/.rules], 1}, {q[_,_], x, x} -> {p[0], -1}, {q[_,_], q[_,a_], p[_]} -> {p[a], -1}, {x, q[_,a_], p[_]} -> {p[a], -1}, {x, x, p[_]} -> {q[0,0], 1}, {_,_,_} -> {x, 0}}])&[vals[[IntegerDigits[i, 7, 3]+1]]], {i, 0, 73-1}]

The ordering in vals defines a mapping of symbolic cell values onto colors. Given a list of initial cell colors for the cellular automaton, the initial conditions for the mobile automaton are given by Flatten[{p[0], Map[p, list], p[0]}] surrounded by x's, with the active cell being placed initially just before the first p[0].

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From Stephen Wolfram: A New Kind of Science [citation]