On Mon, Aug 15, 2011, Artyom Beilis wrote:
From: Soares Chen Ruo Fei <crf@hypershell.org> but it does require that O(1) operations don't
become O(N) operations, or that O(N) operations become O(N^2) operations.
Ok I got what you mean. I think it'll be easier to just remove the decrement function completely. During implementation I also wondered if there is any real use for reverse code point iterator, but since I still got time I just implemented it anyway to leave it for just in case. (Actually it's also because I don't know if there is any way to conditionally let the code point iterator inherit from either std::forward_iterator or std::bidirectional_iterator)
Ok... Now I will make your life even harder :-)
Many Unicode algorithms like segmentation or collation require random access...
So you do need random access or bidirectional iterator.
Bottom line... Don't bother.
It is better to use Unicode in first place :-)
So if that's the case then the only way for the code point iterators of those MBCS adapters to work with these Unicode algorithms is to enable the O(N^2) decrement function. Or is it better to make it yield compilation error and force the developer to manually convert the string into other string adapters before passing to the Unicode algorithms? Random access is quite easy I think once we have bidirectional iterator - just move forward/backward N times. I don't think there is any other way to jump to random location in O(1) without having to decode the string.