# Returns `true` if the string contains only Hex chars
	#
	# ~~~
	# assert "048bf".is_hex  == true
	# assert "ABCDEF".is_hex  == true
	# assert "0G".is_hex == false
	# ~~~
	fun is_hex: Bool
	do
		for i in [0..length[ do
			var c = chars[i]
			if not (c >= 'a' and c <= 'f') and
			   not (c >= 'A' and c <= 'F') and
			   not (c >= '0' and c <= '9') then return false
		end
		return true
	end