basic_string& append(const basic_string& str);
basic_string& append(const basic_string& str, size_type pos, size_type n = npos);
template<class T>
basic_string& append(const T& t);
{ basic_string_view<charT, traits> sv = t; return append(sv.data(), sv.size()); }
template<class T>
basic_string& append(const T& t, size_type pos, size_type n = npos);
basic_string& append(const charT* s, size_type n);
basic_string& append(const charT* s);
basic_string& append(size_type n, charT c);
template<class InputIterator>
basic_string& append(InputIterator first, InputIterator last);
basic_string& append(initializer_list<charT> il);
void push_back(charT c);