# File lib/expression_parser/parser.rb, line 79
    def number
      token = @lexer.get_next_token

      if token.kind == Token::LParen
        value = expression

        expected_rparen = @lexer.get_next_token
        raise 'Unbalanced parenthesis' unless expected_rparen.kind == Token::RParen
      elsif token.kind == Token::Number
        value = token.value
      else
        raise 'Not a number'
      end

      value
    end