From: ptkwt@... (Phil Tomson)
Date: 2003-09-28T15:11:03+09:00
Subject: Re: Thoughts on yield


Here's take 3.  This one seems to work:

module Music
  def initialize
    @notes = []
    @chord_notes=[]
    @tmp_notes = []
  end

  def a(list=@tmp_notes)
    list << "a"
  end

  def b(list=@tmp_notes)
    list << "b"
  end

  def c(list=@tmp_notes)
    list << "c"
  end

  def d(list=@tmp_notes)
    list << "d"
  end
  
  def e(list=@tmp_notes)
    list << "e"
  end
  
  def f(list=@tmp_notes)
    list << "f"
  end
  
  def g(list=@tmp_notes)
    list << "g"
  end

  def clef
    puts "...In Clef..."
    yield
    @notes = @tmp_notes 
    @notes << @chord_notes unless @chord_notes.empty?
    return @notes
  end

  def measure(time)
    puts "...In Measure..."
    yield  
  end

  def chord
    tmpnotes = @tmp_notes.dup
    @tmp_notes.clear
    puts "...In Chord..."
    yield @chord_notes
    @chord_notes = @tmp_notes
    @tmp_notes = tmpnotes
  end

  def notes
    @notes
  end
end

class Song
  include Music

  def define_song(&b)
    instance_eval &b
  end
end

mysong= Song.new 
mysong.define_song {   
  clef do
    measure("4/4") do
      c; d; e; f; g; a; b; c;
      chord do 
        c; d; g; 
      end
    end
  end
}
p mysong.notes


This way the user doesn't even have to define a class, call super and all 
those Ruby details.


Thanks to Joel for the instance_eval suggestion.

Phil