DavidTour fractal

For the grammar.rb library see my Cesàro fractal (here it was included in the davidtour.rb file which is why it didn't need to be separately loaded, Grammar code omitted for brevity).

########################################################
# A David Tour fractal implemented using a
# Lindenmayer System in ruby-processing by Martin Prout
########################################################
require 'davidtour'

class David_Test < Processing::App
  attr_reader :david, :points, :production

  def setup
    size(800, 900)
    @david = DavidTour.new(width * 0.6, height/4)
    @production = david.create_grammar(5)
    @points = david.translate_rules(production)
    no_loop()
  end
  
  def draw()
    background(0)
    stroke(255)
    points.each do |tmp|
      line(*tmp)
    end
  end
end

####################################################
# The DavidTour fractal has been used to study the
# Euclidean travelling salesmam problem
####################################################
class DavidTour

  attr_reader :draw_length, :xpos, :ypos, :theta, :axiom, :grammar
  DELTA = Math::PI/3 # 60 degrees
  
  def initialize xpos, ypos
    @axiom = "FX-XFX-XFX-XFX-XFX-XF"
    @theta  = 0
    @grammar = Grammar.new(axiom)
    grammar.add_rule("F", "!F!-F-!F!")
    grammar.add_rule("X", "!X")
    @draw_length = 15
    @xpos = xpos
    @ypos = ypos
  end

  def create_grammar(gen)  
    @draw_length *= @draw_length * 0.5**gen
    grammar.generate(gen)
  end
  
  def translate_rules(prod)
    swap = false
    points = [] # An empty array to store lines as an array of points
    prod.scan(/./) do |ch|
      case(ch)
      when 'F'
        temp = [xpos, ypos, (@xpos += draw_length * Math.cos(theta)), (@ypos -= draw_length * Math.sin(theta))]
        points.push(temp)      
      when '+'
        @theta += (DELTA)      
      when '-'
        @theta += (swap ? DELTA : -DELTA)
      when '!'
        swap = !swap
      when 'X'    
      else
        puts("character '#{ch}' not in grammar")
      end
    end
    return points
  end
end