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std::basic_ostream<CharT,Traits>::operator=

From cppreference.com
< cpp‎ | io‎ | basic ostream
 
 
 
 
protected:
basic_ostream& operator=( const basic_ostream& rhs ) = delete;
(1)
protected:
basic_ostream& operator=( basic_ostream&& rhs );
(2) (since C++11)
1) The copy assignment operator is protected, and is deleted. Output streams are not CopyAssignable.
2) The move assignment operator exchanges all data members of the base class, except for rdbuf(), with rhs, as if by calling swap(*rhs). This move assignment operator is protected: it is only called by the move assignment operators of the derived movable output stream classes std::basic_ofstream and std::basic_ostringstream, which know how to correctly move-assign the associated streambuffers.

[edit] Parameters

rhs - the basic_ostream object from which to assign to *this

[edit] Example

#include <iostream>
#include <sstream>
#include <utility>
 
int main()
{
    std::ostringstream s;
//  std::cout = s;            // ERROR: copy assignment operator is deleted
//  std::cout = std::move(s); // ERROR: move assignment operator is protected
    s = std::move(std::ostringstream() << 42); // OK, moved through derived
    std::cout << s.str() << '\n';
}

Output:

42

[edit] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2067 C++11 1. the parameter type of overload (1) was basic_ostream&
2. the parameter type of overload (2) was const basic_ostream&&
1. added const
2. removed const