elementary_cellular_automaton.sf

#!/usr/bin/ruby

class Automaton(rule, cells) {

    method init {
        rule = sprintf("%08b", rule).split(1).map{.to_i}.reverse;
    }

    method next {
        var previous = cells.map{_};
        var len = previous.len;
        cells[] = rule[
                    previous.range.map { |i|
                        4*previous[i-1 % len] +
                        2*previous[i]         +
                        previous[i+1 % len]
                    }
                  ]
    }

    method to_s {
        cells.map { _ ? '#' : ' ' }.join('')
    }
}

var size = 20;
var arr = size.of(0);
arr[size/2] = 1;

var auto = Automaton(90, arr);

(size/2).times {
    print "|#{auto}|\n";
    auto.next;
};