std::basic_istream::swap(3)

NAME
std::basic_istream::swap - std::basic_istream::swap

Synopsis
   protected: (since C++11)
   void swap( basic_istream& rhs );
   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.

Parameters
   rhs - different basic_istream object of the same type to swap with

Example
// Run this code
 #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';
 }

Output:
 hello