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std::multiset::swap(3) | C++ Standard Libary | std::multiset::swap(3) |
NAME¶
std::multiset::swap - std::multiset::swap
Synopsis¶
void swap( multiset& other ); (until C++17)
void swap( multiset& other ) noexcept(/* see below */); (since
C++17)
Exchanges the contents of the container with those of other. Does not invoke
any
move, copy, or swap operations on individual elements.
All iterators and references remain valid. The past-the-end iterator is
invalidated.
The Compare objects must be Swappable, and they are exchanged using
unqualified call
to non-member swap.
If
std::allocator_traits<allocator_type>::propagate_on_container_swap::value
is true, then the allocators are exchanged using an unqualified call to
(since
non-member swap. Otherwise, they are not swapped (and if get_allocator() !=
C++11)
other.get_allocator(), the behavior is undefined).
Parameters¶
other - container to exchange the contents with
Return value¶
(none)
Exceptions¶
Any exception thrown by the swap of the Compare objects.
(until C++17)
noexcept specification:
noexcept(std::allocator_traits<Allocator>::is_always_equal::value
(since C++17)
&& std::is_nothrow_swappable<Compare>::value)
Complexity¶
Constant.
Example¶
// Run this code
#include <functional>
#include <iostream>
#include <set>
template<class Os, class Co> Os& operator<<(Os& os, const
Co& co) {
os << "{";
for (auto const& i : co) { os << ' ' << i; }
return os << " } ";
}
int main()
{
std::multiset<int> a1{3, 1, 3, 2}, a2{5, 4, 5};
auto it1 = std::next(a1.begin());
auto it2 = std::next(a2.begin());
const int& ref1 = *(a1.begin());
const int& ref2 = *(a2.begin());
std::cout << a1 << a2 << *it1 << ' ' << *it2
<< ' ' << ref1 << ' ' << ref2 << '\n';
a1.swap(a2);
std::cout << a1 << a2 << *it1 << ' ' << *it2
<< ' ' << ref1 << ' ' << ref2 << '\n';
// Note that every iterator referring to an element in one container before
the swap
// refers to the same element in the other container after the swap. Same is
true
// for references.
struct Cmp : std::less<int> {
int id{};
Cmp(int i) : id{i} { }
};
std::multiset<int, Cmp> s1{ {2, 2, 1, 1}, Cmp{6} }, s2{ {4, 4, 3, 3},
Cmp{9} };
std::cout << s1 << s2 << s1.key_comp().id << ' '
<< s2.key_comp().id << '\n';
s1.swap(s2);
std::cout << s1 << s2 << s1.key_comp().id << ' '
<< s2.key_comp().id << '\n';
// So, comparator objects (Cmp) are also exchanged after the swap.
}
Output:¶
{ 1 2 3 3 } { 4 5 5 } 2 5 1 4
{ 4 5 5 } { 1 2 3 3 } 2 5 1 4
{ 1 1 2 2 } { 3 3 4 4 } 6 9
{ 3 3 4 4 } { 1 1 2 2 } 9 6
See also¶
std::swap(std::multiset) specializes the std::swap algorithm
(function template)
2022.07.31 | http://cppreference.com |