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std::swap(std::basic_string)

Defined in header <string>

Defined in header `<string>`
template< class CharT, class Traits, class Alloc > void swap( std::basic_string<CharT, Traits, Alloc>& lhs, std::basic_string<CharT, Traits, Alloc>& rhs );		(until C++17)
template< class CharT, class Traits, class Alloc > void swap( std::basic_string<CharT, Traits, Alloc>& lhs, std::basic_string<CharT, Traits, Alloc>& rhs ) noexcept(/* see below */);		(since C++17) (until C++20)
template< class CharT, class Traits, class Alloc > constexpr void swap( std::basic_string<CharT, Traits, Alloc>& lhs, std::basic_string<CharT, Traits, Alloc>& rhs ) noexcept(/* see below */);		(since C++20)

template< class CharT, class Traits, class Alloc >
void swap( std::basic_string<CharT, Traits, Alloc>& lhs,
           std::basic_string<CharT, Traits, Alloc>& rhs );

(until C++17)

template< class CharT, class Traits, class Alloc >
void swap( std::basic_string<CharT, Traits, Alloc>& lhs,
           std::basic_string<CharT, Traits, Alloc>& rhs ) noexcept(/* see below */);

(since C++17)
(until C++20)

template< class CharT, class Traits, class Alloc >
constexpr void
    swap( std::basic_string<CharT, Traits, Alloc>& lhs,
          std::basic_string<CharT, Traits, Alloc>& rhs ) noexcept(/* see below */);

(since C++20)

Specializes the std::swap algorithm for std::basic_string. Swaps the contents of lhs and rhs.

Equivalent to lhs.swap(rhs).

Parameters

lhs, rhs

strings whose contents to swap

Return value

(none).

Complexity

Constant.

Exceptions

noexcept specification:

noexcept(noexcept(lhs.swap(rhs)))

(since C++17)

Example

#include <iostream>
#include <string>
 
int main()
{
    std::string a = "AAA";
    std::string b = "BBBB";
 
    std::cout << "Before swap:\n"
                 "a = " << a << "\n"
                 "b = " << b << "\n\n";
 
    std::swap(a, b);
 
    std::cout << "After swap:\n"
                 "a = " << a << "\n"
                 "b = " << b << '\n';
}

Output:

Before swap:
a = AAA
b = BBBB
 
After swap:
a = BBBB
b = AAA

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 2064	C++11	non-member `swap` was noexcept and inconsistent with member `swap`	noexcept removed