If not, how should I do to replace sub-strings? It is a very common use. The substring method could return a new string object rather than modify the old one - C# handles its immutable strings in this way. I'm not so sure having
Strings could be built using a stringstream like approach I don't understand what you mean. Sorry, I wasn't very clear. I meant we would provide a class like std::stringstream that can have strings (of any encoding) added to it using <<. It would convert its contents to a string when the str() method is called (we could pass the required encoding as a parameter/template parameter).
You mean having two classes then, isnt it? It would mean that, yes. One class for the strings (immutable), one class for constructing the strings.
Making the iterator a byte iterator, not a code point iterator, pushes the responsibility for knowing how to handle the variable widthness of the different encodings back onto the user.
So what is your opinion about it? I find it very useless a byte iterator, except for copying. My opinion is also that byte iterators aren't a good idea - if people want to iterate over bytes than a std::vector<byte> would be more appropriate.
We'll definitely need a way to convert to a raw pointer representation (like std::string.c_str()) for interaction with some APIs. Surely Applications often pass string data to APIs as raw pointers - I think that the best way to handle this would be to store strings as contiguous memory within the string class.
These are just my thoughts at the moment as I type. I'll give the matter some more etensive thought before I reply again.