# Returns true if the char is an alpha or a numeric digit
	#
	# ~~~
	# assert 'a'.is_alphanumeric
	# assert 'Z'.is_alphanumeric
	# assert '0'.is_alphanumeric
	# assert '9'.is_alphanumeric
	# assert not '?'.is_alphanumeric
	# ~~~
	#
	# FIXME: Works on ASCII-range only
	fun is_alphanumeric: Bool
	do
		return self.is_numeric or self.is_alpha
	end