std::basic_istream<CharT,Traits>::swap
Min standard notice:
Calls basic_ios::swap(rhs) to swap all data members of the base class except for rdbuf(), and swaps the values of the gcount() counters between *this and rhs. This swap function is protected: it is called by the swap functions of the swappable input stream classes std::basic_ifstream and std::basic_istringstream, which know how to correctly swap the associated streambuffers.
# Declarations
protected:
void swap( basic_istream& rhs );
(since C++11)
# Parameters
rhs: different basic_istream object of the same type to swap with
# Example
#include <iostream>
#include <sstream>
#include <utility>
int main()
{
std::istringstream s1("hello");
std::istringstream s2("bye");
s1.swap(s2); // OK, istringstream has a public swap()
std::swap(s1, s2); // OK, calls s1.swap(s2)
// std::cin.swap(s2); // ERROR: swap is a protected member
std::cout << s1.rdbuf() << '\n';
}