Can you show me some examples with std::streampos?
I am not sure what it is used for and I don't know how to work with it.
I saw in a project in github:
std::streampos pos = ss.tellg();
where ss is std::stringstream.
Why don't we use int pos = ss.tellg(), for example in this case?
Why don't we use int pos = ss.tellg(), for example in this case?
Because std::streampos happens to be the type returned by std::basic_stringstream<char, std::char_traits<char>, std::allocator<char>>::tellg().
Maybe on one computer it's something that converts cleanly to an int, but not on another. By using the correct type, your code is platform-independant.
Also note that std::streampos is the type returned by the tellg() method of that very specific class, not the type returned by tellg() methods everywhere. Other streams might very well return a different type instead of std::streampos, and you should be accounting for that.
The actual cleanest way to choose the correct type for pos is to literally ask the type: "What should I be using to represent positions in the stream?":
std::stringstream::pos_type pos = ss.tellg();
Or just use auto so you don't have to worry about it:
auto pos = some_stream.tellg();