text: from context_free_grammar import Context_Free_Grammar
  
  
  def Grammar():
  	
  	grammar = Context_Free_Grammar()
  	
  	grammar.add_terminal('a', 'b', 'c', '~', ':', 'author', 'title')
  	grammar.add_non_terminal('Text', 'Effect', 'Alpha')
  	grammar.set_start_symbol('Text')
  	
  	grammar.add_production_rule('Text', ['~', 'Effect', ':', 'Text', '~'], ['Alpha'])
  	grammar.add_production_rule('Effect', ['author'], ['title'])
  	grammar.add_production_rule('Alpha', ['a'], ['b'])
  	#grammar.add_production_rule('F', ['(', 'E', ')'], ['id'])
  	
  	return grammar
  
  