gistfile1.rb

      def parse
        expr = assert_expr :expr
        assert_done
        expr
      end


      def assert_expr(name)
        (e = send(name)) && (return e)
        raise Sass::SyntaxError.new("Expected expression, was #{@lexer.done? ? 'end of text' : "#{@lexer.peek.type} token"}.")
      end