# Are all letters in `self` lower-case ?
	#
	# ~~~
	# assert "hello world".is_lower == true
	# assert "%$&%!".is_lower       == true
	# assert "Hello World".is_lower == false
	# ~~~
	fun is_lower: Bool
	do
		for i in [0..length[ do
			var char = chars[i]
			if char.is_upper then return false
		end
		return true
	end