L-system の実装

lsystem.rb

require 'oekaki'

class Lsystem
  def initialize(width, height, title = "L-system")
    @width  = width
    @height = height
    @title = title
    @procedure = ""
    @command = {}
    @rule = {}
    @eval = proc {}
    @po = [0, 0]
    @putout = false
  end
  attr_accessor :dir, :putout
  
  def move(x, y)
    @po = [x, y]
  end
  
  def init(st)
    @procedure = st
  end
  
  def set(st, &block)
    @command[st] = block
  end
  
  def rule(a, r)
    @rule[a] = r
  end
  
  def prologue(&block)
    @eval = block
  end
  
  def generate(n)
    n.times do
      pr = ""
      @procedure.each_char do |c|
        pr += @rule[c] || c
      end
      @procedure = pr
      p pr if @putout
    end
  end
  
  def exec(t)
    stack = []
    @procedure.each_char do |c|
      case c
      when "["
        stack << t.dup
      when "]"
        t = stack.pop
      else
        todo = @command[c]
        raise "#{c} not defined." unless todo
        t.instance_exec(&todo)
      end
    end
  end
  
  def draw(n)
    ob = self
    Oekaki.app width: @width, height: @height, title: @title do
      t = Oekaki::Turtle.new
      ob.generate(n)
      
      draw do
        clear
        t.instance_exec(&ob.instance_variable_get(:@eval))
        t.move(*ob.instance_variable_get(:@po))
        t.dir = ob.dir if ob.dir
        ob.exec(t)
      end
    end
  end
end