Elementary cellular automatonをシミュレートする

eca.rb

class Eca
    attr_reader :cells
    def initialize(role, size = 200)
        @role = role
        @cells = Array.new(size, 0)
        raise if role < 0 || role > 255
    end

    def set(f, offset = nil)
        str = f.is_a?(Integer) ? f.to_s(2) : f.is_a?(String) ? f : nil
        raise if !str
        @cells = Array.new(@cells.size, 0)
        if offset
            raise if offset + str.size > @cells.size
            str.size.times{ |i|
                @cells[offset + i] = str[i]
            }
        else
            raise if str.size > @cells.size
            str.size.times{ |i|
                @cells[@cells.size / 2 - str.size / 2 + i] = str[i]
            }
        end
        @cells
    end

    def step(n = 1)
        n.times{
            new_cells = @cells.dup
            @cells.size.times{|i|
                c = @cells[i - 1, 3] * ""
                c = "0" + c if i == 0
                c = c + "0" if i == @cells.size - 1
                new_cells[i] = @role[c.to_i(2)]
            }
            @cells = new_cells
        }
        @cells
    end

    def inspect
        @cells * ""
    end
end