void swap( unordered_multimap& other ); | (since C++11) (until C++17) | |
void swap( unordered_multimap& 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 Hash
and KeyEqual
objects must be Swappable, and they are exchanged using unqualified calls to non-member swap
.
If | (since C++11) |
other | - | container to exchange the contents with |
(none).
Any exception thrown by the swap of the | (until C++17) |
noexcept specification: noexcept(std::allocator_traits<Allocator>::is_always_equal::value | (since C++17) |
Constant.
#include <iostream> #include <string> #include <utility> #include <unordered_map> // print out a std::pair template <class Os, class U, class V> Os& operator<<(Os& os, const std::pair<U, V>& p) { return os << p.first << ":" << p.second; } // print out a container template <class Os, class Co> Os& operator<<(Os& os, const Co& co) { os << "{"; for (auto const& i : co) { os << ' ' << i; } return os << " }\n"; } int main() { std::unordered_multimap<std::string, std::string> m1 { {"γ", "gamma"}, {"β", "beta"}, {"α", "alpha"}, {"γ", "gamma"}, }, m2 { {"ε", "epsilon"}, {"δ", "delta"}, {"ε", "epsilon"} }; const auto& ref = *(m1.begin()); const auto iter = std::next(m1.cbegin()); std::cout << "──────── before swap ────────\n" << "m1: " << m1 << "m2: " << m2 << "ref: " << ref << "\niter: " << *iter << '\n'; m1.swap(m2); std::cout << "──────── after swap ────────\n" << "m1: " << m1 << "m2: " << m2 << "ref: " << ref << "\niter: " << *iter << '\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. }
Possible output:
──────── before swap ──────── m1: { α:alpha β:beta γ:gamma γ:gamma } m2: { δ:delta ε:epsilon ε:epsilon } ref: α:alpha iter: β:beta ──────── after swap ──────── m1: { δ:delta ε:epsilon ε:epsilon } m2: { α:alpha β:beta γ:gamma γ:gamma } ref: α:alpha iter: β:beta
(C++11) | specializes the std::swap algorithm (function template) |
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