# Return the upper case version of self.
	# If self is not a letter, then return self
	#
	#     assert 'a'.to_upper  == 'A'
	#     assert 'A'.to_upper  == 'A'
	#     assert '$'.to_upper  == '$'
	fun to_upper: Char
	do
		if is_lower then
			return (code_point - ('a'.distance('A'))).code_point
		else
			return self
		end
	end