#     assert u'b'.is_prefix("baqsdb".to_bytes)
	#     assert not u'b'.is_prefix("aqsdb".to_bytes)
	redef fun is_prefix(b) do return b.length != 0 and b.first == self

	redef fun is_prefix(b) do
		if length > b.length then return false
		for i in [0 .. length[ do if self[i] != b[i] then return false
		return true
	end