std::vector<bool,Allocator>::swap

 

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std::swap

eraseerase_if (C++20)(C++20)

operator==operator!=operator<operator>operator<=operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

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Defined in header <vector>
static void swap( reference x, reference y );		(until C++20)
constexpr static void swap( reference x, reference y );		(since C++20)

Swaps the contents of x and y as if by bool b = x; x = y; y = b;.

Parameters

x	-	std::vector<bool>::reference value to swap with y
y	-	std::vector<bool>::reference value to swap with x

Return value

(none)

Complexity

Constant.

Example

Run this code

#include <iostream>
#include <vector>
 
void println(std::string_view fmt, std::vector<bool> const& vb = {})
{
    for (std::cout << fmt; bool const e : vb)
        std::cout << e << ' ';
    std::cout << '\n';
}
 
int main()
{
    println("swap elements of the same vector:");
    std::vector<bool> x { 1, 0 };
    println("before swap, x: ", x);
    x.swap(x[0], x[1]); // same as std::vector<bool>::swap(x[0], x[1]);
    println("after swap,  x: ", x);
 
    println("swap elements of two different vectors:");
    std::vector<bool> y { 0, 0, 1 };
    println("before swap, x: ", x);
    println("before swap, y: ", y);
    y.swap(x[0], y[2]); // same as std::vector<bool>::swap(x[0], y[2]);
    println("after swap,  x: ", x);
    println("after swap,  y: ", y);
}

Output:

swap elements of the same vector:
before swap, x: 1 0 
after swap,  x: 0 1 
swap elements of two different vectors:
before swap, x: 0 1 
before swap, y: 0 0 1 
after swap,  x: 1 1 
after swap,  y: 0 0 0

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 814	C++98	the description of this member function was missing	added

See also

reference	proxy class representing a reference to a single bool (class)
swap	swaps the contents (public member function of std::vector<T,Allocator>)
std::swap(std::vector)	specializes the std::swap algorithm (function template)