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RobotTasksExecuter.start do
  stack :boxes => 5 do
    fetch do
      rotate :rectangle => 60
      pick :speed => 'slow',:height => 15
      rotate :rectangle => -60
      free :speed => 'slow'
    end
    package do
      lock
      seal
    end
  end
end

# A dummy task class
class RobotTask
  # A dummy run task
  # type of task, a margin to indent the output, and some other attributes are passed
  def run(type,margin,attrs={})
    output = "#{margin} Running task '#{type}'"
    output+=", with attributes:" if !attrs.empty?
    puts output
    attrs.each{|key,value| puts "#{margin} --#{key} = #{value}"}
  end
end
 
# A simple tasks executer 
# This code is very basic and could be far optimized
class RobotTasksExecuter
  def initialize
    puts "   **** Robot is working now ****"
    # This is used to indent the output
    @margin = ""
  end
 
  # Start the executer work
  def self.start(&block)
    # Instantiate an executer object and evaluate the DSL code block
    new.instance_eval(&block)
  end
 
  #  All undefined methods will call method_missing
  #  Let's use 'execute' as an alias for method_missing
  alias method_missing execute
 
  # All undefined methods will call this method, because of the aliasing taking place over.
  def execute(type,attrs={})
    @margin += "  "
    RobotTask.new.run(type,@margin,attrs)
    yield if block_given?
    @margin = @margin[0,@margin.length-2]
  end
 
end
 
RobotTasksExecuter.start do
  stack :boxes => 5 do
    fetch do
      rotate :rectangle => 60
      pick :speed => 'slow',:height => 15
      rotate :rectangle => -60
      free :speed => 'slow'
    end
    package do
      lock
      seal
    end
  end
end

   **** Robot is working now ****
   Running task 'stack', with attributes:
   --boxes = 5
     Running task 'fetch'
       Running task 'rotate', with attributes:
       --rectangle = 60
       Running task 'pick', with attributes:
       --speed = slow
       --height = 15
       Running task 'rotate', with attributes:
       --rectangle = -60
       Running task 'free', with attributes:
       --speed = slow
     Running task 'package'
       Running task 'lock'
       Running task 'seal'