# Use a special notation for whitespace characters that are not `'\n'` (LFD) or `' '` (space).
	#
	# ~~~
	# assert "hello".filter_nonprintable == "hello"
	# assert "\r\n\t".filter_nonprintable == "^13\n^9"
	# ~~~
	fun filter_nonprintable: String
	do
		var buf = new Buffer
		for c in self do
			var cp = c.code_point
			if cp < 32 and c != '\n' then
				buf.append "^{cp}"
			else
				buf.add c
			end
		end
		return buf.to_s
	end