# Returns true if the char is a numerical digit
	#
	# ~~~
	# assert '0'.is_numeric
	# assert '9'.is_numeric
	# assert not 'a'.is_numeric
	# assert not '?'.is_numeric
	# ~~~
	#
	# FIXME: Works on ASCII-range only
	fun is_numeric: Bool
	do
		return self >= '0' and self <= '9'
	end