std::set::operator=

 

C++

Language

Standard library headers

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Utilities library

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Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Containers library

array (C++11)

vector

deque

forward_list (C++11)

list

set

multiset

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multimap

unordered_set (C++11)

unordered_multiset (C++11)

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unordered_multimap (C++11)

stack

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std::set

Member functions

set::set

set::~set

set::operator=

set::get_allocator

Iterators

set::beginset::cbegin (C++11)

set::endset::cend (C++11)

set::rbeginset::crbegin (C++11)

set::rendset::crend (C++11)

Capacity

set::empty

set::size

set::max_size

Modifiers

set::clear

set::insert

set::emplace (C++11)

set::emplace_hint (C++11)

set::erase

set::swap

Lookup

set::count

set::find

set::equal_range

set::lower_bound

set::upper_bound

Observers

set::key_comp

set::value_comp

 

set& operator=( const set& other );	(1)
set& operator=( set&& other );	(2)	(since C++11)
set& 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() is true, the target allocator is replaced by a copy of the source allocator. If the target and the source allocators do not compare equal, the target (*this) allocator is used to deallocate the memory, then other's allocator is used to allocate it before copying the elements. (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() is true, the target allocator is replaced by a copy of the source allocator. If it is false and the source and the target allocators do not compare equal, the target cannot take ownership of the source memory and must move-assign each element individually, allocating additional memory using its own allocator as needed.

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 the other.

2) Constant unless std::allocator_traits<allocator_type>::propagate_on_container_move_assignment() is false and the allocators do not compare equal (in which case linear).

3) Linear in the size of ilist.

Exceptions 2) noexcept specification:   noexcept(std::allocator_traits<Allocator>::is_always_equal::value && std::is_nothrow_move_assignable<Compare>::value)

(since C++17)

Example

The following code uses to assign one std::set to another:

Run this code

#include <set>
#include <iostream>
 
void display_sizes(const std::set<int> &nums1,
                   const std::set<int> &nums2,
                   const std::set<int> &nums3)
{
    std::cout << "nums1: " << nums1.size() 
              << " nums2: " << nums2.size()
              << " nums3: " << nums3.size() << '\n';
}
 
int main()
{
    std::set<int> nums1 {3, 1, 4, 6, 5, 9};
    std::set<int> nums2; 
    std::set<int> nums3;
 
    std::cout << "Initially:\n";
    display_sizes(nums1, nums2, nums3);
 
    // copy assignment copies data from nums1 to nums2
    nums2 = nums1;
 
    std::cout << "After assigment:\n"; 
    display_sizes(nums1, nums2, nums3);
 
    // move assignment moves data from nums1 to nums3,
    // modifying both nums1 and nums3
    nums3 = std::move(nums1);
 
    std::cout << "After move assigment:\n"; 
    display_sizes(nums1, nums2, nums3);
}

Output:

Initially:
nums1: 6 nums2: 0 nums3: 0
After assigment:
nums1: 6 nums2: 6 nums3: 0
After move assigment:
nums1: 0 nums2: 6 nums3: 6

See also

(constructor)

constructs the set (public member function)