std::multiset<Key,Compare,Allocator>::operator=

multiset& operator=( const multiset& other );	(1)
	(2)
multiset& operator=( multiset&& other );			(since C++11) (until C++17)
multiset& operator=( multiset&& other ) noexcept(/* see below */);			(since C++17)
multiset& operator=( std::initializer_list<value_type> ilist );		(3)	(since C++11)

Replaces the contents of the container.

1) Copy assignment operator. Replaces the contents with a copy of the contents of other.

If std::allocator_traits<allocator_type>::propagate_on_container_copy_assignment::value is true, the allocator of *this is replaced by a copy of that of other. If the allocator of *this after assignment would compare unequal to its old value, the old allocator is used to deallocate the memory, then the new allocator is used to allocate it before copying the elements. Otherwise, the memory owned by *this may be reused when possible. In any case, the elements originally belong to *this may be either destroyed or replaced by element-wise copy-assignment.

(since C++11)

2) Move assignment operator. Replaces the contents with those of other using move semantics (i.e. the data in other is moved from other into this container). other is in a valid but unspecified state afterwards.

If std::allocator_traits<allocator_type>::propagate_on_container_move_assignment::value is true, the allocator of *this is replaced by a copy of that of other. If it is false and the allocators of *this and other do not compare equal, *this cannot take ownership of the memory owned by other and must move-assign each element individually, allocating additional memory using its own allocator as needed. In any case, all elements originally belong to *this are either destroyed or replaced by element-wise move-assignment.

3) Replaces the contents with those identified by initializer list ilist.

Parameters

other	-	another container to use as data source
ilist	-	initializer list to use as data source

Return value

*this

Complexity

1) Linear in the size of *this and other.

2) Linear in the size of *this unless the allocators do not compare equal and do not propagate, in which case linear in the size of *this and other.

3)

O(NlogN)

in general, where

N

is size() + ilist.size(). Linear if ilist is sorted with respect to value_comp().

Exceptions

May throw implementation-defined exceptions.	(until C++17)
1,3) May throw implementation-defined exceptions. 2) `noexcept` specification: noexcept(std::allocator_traits<Allocator>::is_always_equal::value && std::is_nothrow_move_assignable<Compare>::value)	(since C++17)

Notes

After container move assignment (overload (2)), unless element-wise move assignment is forced by incompatible allocators, references, pointers, and iterators (other than the end iterator) to other remain valid, but refer to elements that are now in *this. The current standard makes this guarantee via the blanket statement in [container.requirements.general]/12, and a more direct guarantee is under consideration via LWG 2321.

Example

The following code uses operator= to assign one std::multiset to another:

Run this code

#include <set>
#include <iterator>
#include <iostream>
 
void print(auto const comment, auto const& container)
{
    auto size = std::size(container);
    std::cout << comment << "{ ";
    for (auto const& element: container)
        std::cout << element << (--size ? ", " : " ");
    std::cout << "}\n";
}
 
int main()
{
    std::multiset<int> x { 1, 2, 3 }, y, z;
    const auto w = { 4, 5, 6, 7 };
 
    std::cout << "Initially:\n";
    print("x = ", x);
    print("y = ", y);
    print("z = ", z);
 
    std::cout << "Copy assignment copies data from x to y:\n";
    y = x;
    print("x = ", x);
    print("y = ", y);
 
    std::cout << "Move assignment moves data from x to z, modifying both x and z:\n";
    z = std::move(x);
    print("x = ", x);
    print("z = ", z);
 
    std::cout << "Assignment of initializer_list w to z:\n";
    z = w;
    print("w = ", w);
    print("z = ", z);
}

Output:

Initially:
x = { 1, 2, 3 }
y = { }
z = { }
Copy assignment copies data from x to y:
x = { 1, 2, 3 }
y = { 1, 2, 3 }
Move assignment moves data from x to z, modifying both x and z:
x = { }
z = { 1, 2, 3 }
Assignment of initializer_list w to z:
w = { 4, 5, 6, 7 }
z = { 4, 5, 6, 7 }

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Sequence
array (C++11)
vector
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forward_list (C++11)
list
Associative
set
multiset
map
multimap
Unordered associative
unordered_set (C++11)
unordered_multiset (C++11)
unordered_map (C++11)
unordered_multimap (C++11)
Adaptors
stack
queue
priority_queue
Views
span (C++20)

Member functions
multiset::multiset
multiset::~multiset
multiset::operator=
multiset::get_allocator
Iterators
multiset::beginmultiset::cbegin (C++11)
multiset::endmultiset::cend (C++11)
multiset::rbeginmultiset::crbegin (C++11)
multiset::rendmultiset::crend (C++11)
Capacity
multiset::empty
multiset::size
multiset::max_size
Modifiers
multiset::clear
multiset::insert
multiset::emplace (C++11)
multiset::emplace_hint (C++11)
multiset::erase
multiset::swap
multiset::extract (C++17)
multiset::merge (C++17)
Lookup
multiset::count
multiset::find
multiset::contains (C++20)
multiset::equal_range
multiset::lower_bound
multiset::upper_bound
Observers
multiset::key_comp
multiset::value_comp
Non-member functions
std::swap
erase_if (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)
Deduction guides(C++17)