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

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< cpp‎ | container‎ | multiset

 
C++
 
Containers library
 
std::multiset
Member functions
multiset::multiset
Iterators
(C++11)
(C++11)
(C++11)
(C++11)
Capacity
Modifiers
(C++23)
(C++11)
(C++11)
(C++17)
(C++17)
Lookup
(C++20)
Observers
Non-member functions
(C++20)
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)
Deduction guides(C++17)
 
(1)
multiset();
 (until C++11)
multiset()
        : multiset(Compare()) { }
 (since C++11)
explicit multiset( const Compare& comp,
                   const Allocator& alloc = Allocator() );
 (2)
explicit multiset( const Allocator& alloc );
 (3) (since C++11)
template< class InputIt >

multiset( InputIt first, InputIt last,
          const Compare& comp = Compare(),

          const Allocator& alloc = Allocator() );
 (4)
template< class InputIt >

multiset( InputIt first, InputIt last,
          const Allocator& alloc )

        : multiset(first, last, Compare(), alloc) { }
 (5) (since C++14)
multiset( const multiset& other );
 (6)
multiset( const multiset& other, const Allocator& alloc );
 (7) (since C++11)
multiset( multiset&& other );
 (8) (since C++11)
multiset( multiset&& other, const Allocator& alloc );
 (9) (since C++11)
multiset( std::initializer_list<value_type> init,

          const Compare& comp = Compare(),

          const Allocator& alloc = Allocator() );
 (10) (since C++11)
multiset( std::initializer_list<value_type> init,

          const Allocator& alloc )

        : multiset(init, Compare(), alloc) { }
 (11) (since C++14)
template< container-compatible-range<value_type> R >

multiset( std::from_range_t, R&& rg,
          const Compare& comp = Compare(),

          const Allocator& alloc = Allocator() );
 (12) (since C++23)
template< container-compatible-range<value_type> R >

multiset( std::from_range_t, R&& rg,
          const Allocator& alloc )

        : multiset(std::from_range, std::forward<R>(rg), Compare(), alloc) { }
 (13) (since C++23)

Constructs new container from a variety of data sources and optionally using user supplied allocator alloc or comparison function object comp.

1-3) Constructs an empty container.
4-5) Constructs the container with the contents of the range [first, last).
6-7) Copy constructor. Constructs the container with the copy of the contents of other.

If alloc is not provided, allocator is obtained by calling std::allocator_traits<allocator_type>::
    select_on_container_copy_construction(other.get_allocator()).

(since C++11)

During class template argument deduction, only the first argument contributes to the deduction of the container's Allocator template parameter.

(since C++23)
8-9) Move constructor. Constructs the container with the contents of other using move semantics. If alloc is not provided, allocator is obtained by move-construction from the allocator belonging to other.

During class template argument deduction, only the first argument contributes to the deduction of the container's Allocator template parameter.

(since C++23)
10-11) Initializer-list constructor. Constructs the container with the contents of the initializer list init.
12-13) Constructs the container with the contents of rg.

Parameters

alloc - allocator to use for all memory allocations of this container
comp - comparison function object to use for all comparisons of keys
first, last - the range [first, last) to copy the elements from
rg - a container compatible range, that is, an input_range whose elements are convertible to value_type
other - another container to be used as source to initialize the elements of the container with
init - initializer list to initialize the elements of the container with
Type requirements
-
InputIt must meet the requirements of LegacyInputIterator.
-
Compare must meet the requirements of Compare.
-
Allocator must meet the requirements of Allocator.

Complexity

1-3) Constant.
4-5) N·log(N) where N = std::distance(first, last) in general, linear in N if the range is already sorted by value_comp().
6-7) Linear in size of other.
8-9) Constant. If alloc is given and alloc != other.get_allocator(), then linear.
10-11) N·log(N) where N = init.size() in general, linear in N if init is already sorted by value_comp().
12-13) N·log(N) where N = ranges::distance(rg) in general, linear in N if the range is already sorted by value_comp().

Exceptions

Calls to Allocator::allocate may throw.

Notes

After container move construction (overload (8-9)), 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.rev.reqmts]/17, and a more direct guarantee is under consideration via LWG issue 2321.

Although not formally required until C++23, some implementations has already put the template parameter Allocator into non-deduced contexts in earlier modes.

Feature-test macro Value Std Comment
__cpp_lib_containers_ranges 202202L (C++23) Ranges-aware construction and insertion; overloads (12,13)

Example

Run this code
#include <iostream>
#include <set>
#include <string_view>
 
void print(const std::string_view name, const std::multiset<int>& ms)
{
    std::cout << name << ": ";
    for (auto element : ms)
        std::cout << element << ' ';
    std::cout << '\n';
}
 
int main()
{
    // (1) Default constructor
    std::multiset<int> a;
    a.insert(4);
    a.insert(3);
    a.insert(2);
    a.insert(1);
    print("a", a);
 
    // (4) Iterator constructor
    std::multiset<int> b(a.begin(), a.find(3));
    print("b", b);
 
    // (6) Copy constructor
    std::multiset<int> c(a);
    print("c", c);
 
    // (8) Move constructor
    std::multiset<int> d(std::move(a));
    print("d", d);
 
    // (10) Initializer list constructor
    std::multiset<int> e{3, 2, 1, 2, 4, 7, 3};
    print("e", e);
}

Output: 

a: 1 2 3 4
b: 1 2
c: 1 2 3 4
d: 1 2 3 4
e: 1 2 2 3 3 4 7

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 2193 C++11 the default constructor is explicit made non-explicit

See also

 assigns values to the container
(public member function)
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