29 Input/output library [input.output]

29.10 File-based streams [file.streams]

29.10.5 Class template basic_­fstream [fstream]

29.10.5.3 Assignment and swap [fstream.assign]

void swap(basic_fstream& rhs);
Effects: Exchanges the state of *this and rhs by calling basic_­iostream<charT,traits>​::​swap(rhs) and sb.swap(rhs.sb).
template<class charT, class traits> void swap(basic_fstream<charT, traits>& x, basic_fstream<charT, traits>& y);
Effects: Equivalent to: x.swap(y).