def EQL?(sample) 
      @it.eql?(sample) && sample.eql?(@it) && (@it.hash == sample.hash) &&
      ({@it => true}.has_key? sample)
    end
def EQL?(sample) 
      @it.eql?(sample) && sample.eql?(@it) && (@it.hash == sample.hash) &&
      ({@it => true}.has_key? sample)
    end
true if can use for hash-key