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std::swap(std::basic_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)

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 <string>
#include <iostream>
 
int main() 
{
    std::string a = "AAAA";
    std::string b = "BBB";
 
    std::cout << "before swap" << '\n';
    std::cout << "a: " << a << '\n';
    std::cout << "b: " << b << '\n';
 
    std::swap(a,b);
 
    std::cout << "after swap" << '\n';
    std::cout << "a: " << a << '\n';
    std::cout << "b: " << b << '\n';
}

Output:

before swap
a: AAAA
b: BBB
after swap
a: BBB
b: AAAA

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

See also

swaps the contents
(public member function)

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