math grammar

grammar Arithmetic
  rule sum_operand
    mdiv_operand (sumoperator mdiv_operand)* {
      def content
        expr_cont
      end
    }
  end
  
  rule mdiv_operand
    exp_operand (mdivoperator exp_operand)* {
      def content
        expr_cont
      end
    }
  end
  
  rule exp_operand
    operand (expoperator operand)* {
      def content
        expr_cont
      end
    }
  end
  
  rule operand
    fn_num / '(' sum_operand ')' {
      def content
        elements[1] ? elements[1].content : elements[0].content
      end
    }
  end
  
  rule fn_num
    num / fnname '(' sum_operand ')' {
      def content
        elements[1].terminal? ? [elements[0].text_value, elements[2].content] : elements[0].content
      end
    }
  end
  
  rule fnname
    [a-z_] [_a-z0-9]+ {
      def content
        text_value
      end
    }
  end
  
  rule num
    '-'? ('0x' [0-9a-fA-F]+ / '0b' [01]+ / ([0-9]+ ('.' [0-9]+)?) / ([Pp] [Ii]) / 'π' / [Ee] / [Ii]) {
      def content
        if %w[pi e i π].include?(text_value.downcase)
          if "i" == text_value.downcase
            return Complex(0, 1)
          else
            return Math.const_get((text_value == 'π' ? 'pi' : text_value).upcase.to_sym)
          end
        end
        case text_value[0...2]
        when "0."
          text_value.to_f
        when /0./
          Integer(text_value).to_f
        else
          text_value.to_f
        end
      end
    }
  end
  
  rule mdivoperator
    [\/\*] {
      def content
        text_value.to_sym
      end
    }
  end
  
  rule sumoperator
    [+\-] {
      def content
        text_value.to_sym
      end
    }
  end
  
  rule expoperator
    [\^] {
      def content
        text_value.to_sym
      end
    }
  end
end