def define_rule(name, trace, productions)
      rules[name.to_sym] = Rule.new(name.to_sym, construct_rule(productions), trace)
    end
def define_rule(name, trace, productions)
      rules[name.to_sym] = Rule.new(name.to_sym, construct_rule(productions), trace)
    end
Defines a static rule in the grammar.

 @param [Symbol] name
 @param [Array] productions