redef fun to_upper do
		var ret = clone
		ret.upper
		return ret
	end

	redef fun to_upper do return new Concat(_left.to_upper, _right.to_upper)

	redef fun to_upper
	do
		var outstr = new FlatBuffer.with_capacity(self._byte_length + 1)

		var mylen = _length
		var pos = 0

		while pos < mylen do
			outstr.add(chars[pos].to_upper)
			pos += 1
		end

		return outstr.to_s
	end