The problem with const string& is that the resulting string is not interned - e.g. one copy in memory, which would later allow to save memory, compare by pointe

The problem with const string& is that the resulting string is not interned - e.g. one copy in memory, which would later allow to save memory, compare by pointer equality (eq), etc. I understand that the language cannot express it, and that's why other languages (such as lua) do it the right way - immutable strings all the way, or at least by default (NSString)