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Difference between revisions of "cpp/container/multiset"

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< cpp‎ | container
m (Text replace - "{{tdcl list begin}} {{tdcl list h1 | Member types}}" to "===Member types=== {{tdcl list begin}}")
m (→‎Member types: ~Type)
 
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{{cpp/title|multiset}}
 
{{cpp/title|multiset}}
−
{{cpp/container/multiset/sidebar}}
+
{{cpp/container/multiset/navbar}}
−
{{ddcl | header=set |
+
{{dcl begin}}
 +
{{dcl header|set}}
 +
{{dcl|num=1|1=
 
template<
 
template<
 
     class Key,
 
     class Key,
−
     class Compare {{=}} std::less<Key>,
+
     class Compare = std::less<Key>,
−
     class Allocator {{=}} std::allocator<Key>
+
     class Allocator = std::allocator<Key>
 
> class multiset;
 
> class multiset;
−
}}  
+
}}
 +
{{dcl|num=2|since=c++17|1=
 +
namespace pmr {
 +
    template<
 +
        class Key,
 +
        class Compare = std::less<Key>
 +
    > using multiset = std::multiset<Key, Compare, std::pmr::polymorphic_allocator<Key>>;
 +
}
 +
}}
 +
{{dcl end}}
  
−
Multiset is an associative container that contains a sorted set of objects of type Key. Sorting is done using the key comparison function Compare.  
+
{{tt|std::multiset}} is an associative container that contains a sorted set of objects of type Key. Unlike set, multiple keys with equivalent values are allowed. Sorting is done using the key comparison function Compare. Search, insertion, and removal operations have logarithmic complexity.
  
−
===Member types===
+
Everywhere the standard library uses the {{named req|Compare}} requirements, equivalence is determined by using the equivalence relation as described on {{named req|Compare}}. In imprecise terms, two objects {{c|a}} and {{c|b}} are considered equivalent if neither compares less than the other: {{c|!comp(a, b) && !comp(b, a)}}.
−
{{tdcl list begin}}
+
−
{{tdcl list hitem | Member type | Definition}}
+
−
{{tdcl list template | cpp/container/tdcl list key_type | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list value_type | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list size_type | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list difference_type | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list key_compare | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list value_compare | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list allocator_type | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list reference | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list const_reference | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list pointer | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list const_pointer | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list iterator | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list const_iterator | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list reverse_iterator | multiset}}
+
−
{{tdcl list template | cpp/container/tdcl list const_reverse_iterator | multiset}}
+
−
{{tdcl list end}}
+
  
 +
{{rrev|since=c++11|
 +
The order of the elements that compare equivalent is the order of insertion and does not change.}}
  
 +
{{tt|std::multiset}} meets the requirements of {{named req|Container}}, {{named req|AllocatorAwareContainer}}, {{named req|AssociativeContainer}} and {{named req|ReversibleContainer}}.
 +
 +
===Template parameters===
 +
{{todo|Add descriptions of the template parameters.}}
 +
 +
===Member types===
 +
{{dsc begin}}
 +
{{dsc hitem|Type|Definition}}
 +
{{dsc inc|cpp/container/dsc key_type|multiset}}
 +
{{dsc inc|cpp/container/dsc value_type|multiset}}
 +
{{dsc inc|cpp/container/dsc size_type|multiset}}
 +
{{dsc inc|cpp/container/dsc difference_type|multiset}}
 +
{{dsc inc|cpp/container/dsc key_compare|multiset}}
 +
{{dsc inc|cpp/container/dsc value_compare2|multiset}}
 +
{{dsc inc|cpp/container/dsc allocator_type|multiset}}
 +
{{dsc inc|cpp/container/dsc reference|multiset}}
 +
{{dsc inc|cpp/container/dsc const_reference|multiset}}
 +
{{dsc inc|cpp/container/dsc pointer|multiset}}
 +
{{dsc inc|cpp/container/dsc const_pointer|multiset}}
 +
{{dsc inc|cpp/container/dsc iterator|multiset}}
 +
{{dsc inc|cpp/container/dsc const_iterator|multiset}}
 +
{{dsc inc|cpp/container/dsc reverse_iterator|multiset}}
 +
{{dsc inc|cpp/container/dsc const_reverse_iterator|multiset}}
 +
{{dsc inc|cpp/container/dsc node_type|multiset}}
 +
{{dsc end}}
  
 
===Member functions===
 
===Member functions===
−
{{dcl list begin}}
+
{{dsc begin}}
−
{{dcl list template | cpp/container/dcl list constructor | multiset}}
+
{{dsc inc|cpp/container/dsc constructor|multiset}}
−
{{dcl list template | cpp/container/dcl list destructor | multiset}}
+
{{dsc inc|cpp/container/dsc destructor|multiset}}
−
{{dcl list template | cpp/container/dcl list operator{{=}} | multiset}}
+
{{dsc inc|cpp/container/dsc operator{{=}}|multiset}}
−
{{dcl list template | cpp/container/dcl list get_allocator | multiset}}
+
{{dsc inc|cpp/container/dsc get_allocator|multiset}}
 +
 
 +
{{dsc h2|Iterators}}
 +
{{dsc inc|cpp/container/dsc begin|multiset}}
 +
{{dsc inc|cpp/container/dsc end|multiset}}
 +
{{dsc inc|cpp/container/dsc rbegin|multiset}}
 +
{{dsc inc|cpp/container/dsc rend|multiset}}
 +
 
 +
{{dsc h2|Capacity}}
 +
{{dsc inc|cpp/container/dsc empty|multiset}}
 +
{{dsc inc|cpp/container/dsc size|multiset}}
 +
{{dsc inc|cpp/container/dsc max_size|multiset}}
 +
 
 +
{{dsc h2|Modifiers}}
 +
{{dsc inc|cpp/container/dsc clear|multiset}}
 +
{{dsc inc|cpp/container/dsc insert|multiset}}
 +
{{dsc inc|cpp/container/dsc insert_range|multiset}}
 +
{{dsc inc|cpp/container/dsc emplace|multiset}}
 +
{{dsc inc|cpp/container/dsc emplace_hint|multiset}}
 +
{{dsc inc|cpp/container/dsc erase|multiset}}
 +
{{dsc inc|cpp/container/dsc swap|multiset}}
 +
{{dsc inc|cpp/container/dsc extract|multiset}}
 +
{{dsc inc|cpp/container/dsc merge|multiset}}
 +
 
 +
{{dsc h2|Lookup}}
 +
{{dsc inc|cpp/container/dsc count|multiset}}
 +
{{dsc inc|cpp/container/dsc find|multiset}}
 +
{{dsc inc|cpp/container/dsc contains|multiset}}
 +
{{dsc inc|cpp/container/dsc equal_range|multiset}}
 +
{{dsc inc|cpp/container/dsc lower_bound|multiset}}
 +
{{dsc inc|cpp/container/dsc upper_bound|multiset}}
 +
 
 +
{{dsc h2|Observers}}
 +
{{dsc inc|cpp/container/dsc key_comp|multiset}}
 +
{{dsc inc|cpp/container/dsc value_comp|multiset}}
 +
{{dsc end}}
 +
 
 +
===Non-member functions===
 +
{{dsc begin}}
 +
{{dsc inc|cpp/container/dsc operator_cmp|multiset}}
 +
{{dsc inc|cpp/container/dsc swap2|multiset}}
 +
{{dsc inc|cpp/container/dsc erase_if|multiset}}
 +
{{dsc end}}
 +
 
 +
{{rrev|since=c++17|
 +
==={{rl|deduction guides|Deduction guides}}===
 +
}}
  
−
{{dcl list h2 | Iterators}}
+
===Notes===
−
{{dcl list template | cpp/container/dcl list begin | multiset}}
+
{{cpp/container/assoc_note}}
−
{{dcl list template | cpp/container/dcl list end | multiset}}
+
−
{{dcl list template | cpp/container/dcl list rbegin | multiset}}
+
−
{{dcl list template | cpp/container/dcl list rend | multiset}}
+
  
−
{{dcl list h2 | Capacity}}
+
{{ftm begin|std=1|comment=1}}
−
{{dcl list template | cpp/container/dcl list empty | multiset}}
+
{{ftm|__cpp_lib_containers_ranges|value=202202L|std=C++23|Ranges construction and insertion for containers}}
−
{{dcl list template | cpp/container/dcl list size | multiset}}
+
{{ftm end}}
−
{{dcl list template | cpp/container/dcl list max_size | multiset}}
+
  
−
{{dcl list h2 | Modifiers}}
+
===Example===
−
{{dcl list template | cpp/container/dcl list clear | multiset}}
+
{{example}}
−
{{dcl list template | cpp/container/dcl list insert | multiset}}
+
−
{{dcl list template | cpp/container/dcl list emplace | multiset}}
+
−
{{dcl list template | cpp/container/dcl list emplace_hint | multiset}}
+
−
{{dcl list template | cpp/container/dcl list erase | multiset}}
+
−
{{dcl list template | cpp/container/dcl list swap | multiset}}
+
  
−
{{dcl list h2 | Lookup}}
+
===Defect reports===
−
{{dcl list template | cpp/container/dcl list count | multiset}}
+
{{dr list begin}}
−
{{dcl list template | cpp/container/dcl list find | multiset}}
+
{{dr list item|wg=lwg|dr=103|std=C++98|before=iterator allows modification of keys|after=iterator made constant}}
−
{{dcl list template | cpp/container/dcl list equal_range | multiset}}
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{{dr list item|wg=lwg|dr=230|std=C++98|before={{tt|Key}} was not required to be {{named req|CopyConstructible}}<br>(a key of type {{tt|Key}} might not be able to be constructed)|after={{tt|Key}} is also required to<br>be {{named req|CopyConstructible}}}}
−
{{dcl list template | cpp/container/dcl list lower_bound | multiset}}
+
{{dr list end}}
−
{{dcl list template | cpp/container/dcl list upper_bound | multiset}}
+
  
−
{{dcl list h2 | Observers}}
+
===See also===
−
{{dcl list template | cpp/container/dcl list key_comp | multiset}}
+
{{dsc begin}}
−
{{dcl list template | cpp/container/dcl list value_comp | multiset}}
+
{{dsc inc|cpp/container/dsc set}}
 +
{{dsc inc|cpp/container/dsc unordered_multiset}}
 +
{{dsc inc|cpp/container/dsc flat_multiset}}
 +
{{dsc end}}
  
−
{{dcl list h1 | Non-member functions}}
+
{{langlinks|de|es|fr|it|ja|pl|pt|ru|zh}}
−
{{dcl list template | cpp/container/dcl list operator_comp | multiset}}
+
−
{{dcl list template | cpp/container/dcl list std_swap | multiset}}
+
−
{{dcl list end}}
+

Latest revision as of 15:48, 1 November 2024

 
C++
 
Containers library
 
std::multiset
Member functions
Non-member functions
(until C++20)(until C++20)(until C++20)(until C++20)(until C++20)
Deduction guides(C++17)
 
Defined in header <set>
template<

    class Key,
    class Compare = std::less<Key>,
    class Allocator = std::allocator<Key>

> class multiset;
 (1)
namespace pmr {

    template<
        class Key,
        class Compare = std::less<Key>
    > using multiset = std::multiset<Key, Compare, std::pmr::polymorphic_allocator<Key>>;

}
 (2) (since C++17)

std::multiset is an associative container that contains a sorted set of objects of type Key. Unlike set, multiple keys with equivalent values are allowed. Sorting is done using the key comparison function Compare. Search, insertion, and removal operations have logarithmic complexity.

Everywhere the standard library uses the Compare requirements, equivalence is determined by using the equivalence relation as described on Compare. In imprecise terms, two objects a and b are considered equivalent if neither compares less than the other: !comp(a, b) && !comp(b, a).

The order of the elements that compare equivalent is the order of insertion and does not change.

(since C++11)

std::multiset meets the requirements of Container, AllocatorAwareContainer, AssociativeContainer and ReversibleContainer.

Contents

[edit] Template parameters

This section is incomplete
Reason: Add descriptions of the template parameters.

[edit] Member types

Type Definition
key_type Key[edit]
value_type Key[edit]
size_type Unsigned integer type (usually std::size_t)[edit]
difference_type Signed integer type (usually std::ptrdiff_t)[edit]
key_compare Compare[edit]
value_compare Compare[edit]
allocator_type Allocator[edit]
reference value_type&[edit]
const_reference const value_type&[edit]
pointer

Allocator::pointer

(until C++11)

std::allocator_traits<Allocator>::pointer

(since C++11)
[edit]
const_pointer

Allocator::const_pointer

(until C++11)

std::allocator_traits<Allocator>::const_pointer

(since C++11)
[edit]
iterator Constant LegacyBidirectionalIterator to value_type[edit]
const_iterator LegacyBidirectionalIterator to const value_type[edit]
reverse_iterator std::reverse_iterator<iterator>[edit]
const_reverse_iterator std::reverse_iterator<const_iterator>[edit]
node_type (since C++17) a specialization of node handle representing a container node[edit]

[edit] Member functions

 constructs the multiset
(public member function) [edit]
destructs the multiset
(public member function) [edit]
assigns values to the container
(public member function) [edit]
returns the associated allocator
(public member function) [edit]
Iterators
(C++11)
 returns an iterator to the beginning
(public member function) [edit]
(C++11)
 returns an iterator to the end
(public member function) [edit]
(C++11)
 returns a reverse iterator to the beginning
(public member function) [edit]
(C++11)
 returns a reverse iterator to the end
(public member function) [edit]
Capacity
checks whether the container is empty
(public member function) [edit]
returns the number of elements
(public member function) [edit]
returns the maximum possible number of elements
(public member function) [edit]
Modifiers
clears the contents
(public member function) [edit]
inserts elements or nodes(since C++17)
(public member function) [edit]
(C++23)
 inserts a range of elements
(public member function) [edit]
(C++11)
 constructs element in-place
(public member function) [edit]
(C++11)
 constructs elements in-place using a hint
(public member function) [edit]
erases elements
(public member function) [edit]
swaps the contents
(public member function) [edit]
(C++17)
 extracts nodes from the container
(public member function) [edit]
(C++17)
 splices nodes from another container
(public member function) [edit]
Lookup
returns the number of elements matching specific key
(public member function) [edit]
finds element with specific key
(public member function) [edit]
(C++20)
 checks if the container contains element with specific key
(public member function) [edit]
returns range of elements matching a specific key
(public member function) [edit]
returns an iterator to the first element not less than the given key
(public member function) [edit]
returns an iterator to the first element greater than the given key
(public member function) [edit]
Observers
returns the function that compares keys
(public member function) [edit]
returns the function that compares keys in objects of type value_type
(public member function) [edit]

[edit] Non-member functions

(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(C++20)
 lexicographically compares the values of two multisets
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]
(C++20)
 erases all elements satisfying specific criteria
(function template) [edit]

Deduction guides

 (since C++17)

[edit] Notes

The member types iterator and const_iterator may be aliases to the same type. This means defining a pair of function overloads using the two types as parameter types may violate the One Definition Rule. Since iterator is convertible to const_iterator, a single function with a const_iterator as parameter type will work instead.

Feature-test macro Value Std Feature
__cpp_lib_containers_ranges 202202L (C++23) Ranges construction and insertion for containers

[edit] Example

This section is incomplete
Reason: no example

[edit] 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 103 C++98 iterator allows modification of keys iterator made constant
LWG 230 C++98 Key was not required to be CopyConstructible
(a key of type Key might not be able to be constructed) 		Key is also required to
be CopyConstructible

[edit] See also

 collection of unique keys, sorted by keys
(class template) [edit]
(C++11)
 collection of keys, hashed by keys
(class template) [edit]
(C++23)
 adapts a container to provide a collection of keys, sorted by keys
(class template) [edit]
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