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Difference between revisions of "cpp/container/flat multiset"

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< cpp‎ | container
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{{cpp/title|flat_multiset}}
 
{{cpp/title|flat_multiset}}
 
{{cpp/container/flat_multiset/navbar}}
 
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{{ddcl|header=flat_multiset|1=
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{{ddcl|header=flat_set|since=c++23|1=
 
template<
 
template<
 
     class Key,
 
     class Key,
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The flat multiset is a [[cpp/container#Container adaptors|container adaptor]] that gives the functionality of an associative container that stores a sorted set of objects of type {{tt|Key}}. Unlike {{lc|std::flat_set}}, multiple keys with equivalent values are allowed. Sorting is done using the key comparison function {{tt|Compare}}.
 
The flat multiset is a [[cpp/container#Container adaptors|container adaptor]] that gives the functionality of an associative container that stores a sorted set of objects of type {{tt|Key}}. Unlike {{lc|std::flat_set}}, multiple keys with equivalent values are allowed. Sorting is done using the key comparison function {{tt|Compare}}.
 +
 +
The class template {{tt|flat_multiset}} acts as a wrapper to the underlying sorted container passed as object of type {{tt|KeyContainer}}.
  
 
Everywhere the standard library uses the {{named req|Compare}} requirements, uniqueness is determined by using the equivalence relation. Informally, two objects {{c|a}} and {{c|b}} are considered equivalent if neither compares less than the other: {{c|!comp(a, b) && !comp(b, a)}}.
 
Everywhere the standard library uses the {{named req|Compare}} requirements, uniqueness is determined by using the equivalence relation. Informally, two objects {{c|a}} and {{c|b}} are considered equivalent if neither compares less than the other: {{c|!comp(a, b) && !comp(b, a)}}.
  
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The class template {{tt|flat_multiset}} acts as a wrapper to the underlying sorted container passed as object of type {{tt|KeyContainer}}.
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<!--For std::multimap the following is true (what about flat_multiset?): The order of the key pairs whose keys compare equivalent is the order of insertion and does not change.-->
  
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{{tt|std::flat_multiset}} meets the requirements of {{named req|Container}}, {{named req|ReversibleContainer}}, optional container requirements<!--TODO: give a link to N4950.24.2.2.4-->, and all requirements of {{named req|AssociativeContainer}} (including logarithmic search complexity), except that:
+
{{tt|std::flat_multiset}} meets the requirements of {{named req|Container}}, {{named req|ReversibleContainer}}, {{lsd|cpp/named_req/Container#Optional container requirements}}, and all requirements of {{named req|AssociativeContainer}} (including logarithmic search complexity), except that:
 
* requirements related to nodes are not applicable,
 
* requirements related to nodes are not applicable,
 
* iterator invalidation requirements differ, <!--TODO: describe iterator/pointer invalidation properties, maybe per each function -->
 
* iterator invalidation requirements differ, <!--TODO: describe iterator/pointer invalidation properties, maybe per each function -->
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===Template parameters===
 
===Template parameters===
 
{{par begin}}
 
{{par begin}}
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{{par|Key|The type of the stored elements. The behavior is undefined if {{tt|Key}} is not the same type as {{tt|KeyContainer::value_type}}.}}
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{{par|Key|The type of the stored elements. The program is ill-formed if {{tt|Key}} is not the same type as {{tt|KeyContainer::value_type}}.}}
 
{{par|Compare|A {{named req|Compare}} type providing a strict weak ordering.
 
{{par|Compare|A {{named req|Compare}} type providing a strict weak ordering.
 
{{par|KeyContainer|The type of the underlying {{named req|SequenceContainer}} to store the elements. The iterators of such container should satisfy {{named req|RandomAccessIterator}} or model {{lconcept|random_access_iterator}}.
 
{{par|KeyContainer|The type of the underlying {{named req|SequenceContainer}} to store the elements. The iterators of such container should satisfy {{named req|RandomAccessIterator}} or model {{lconcept|random_access_iterator}}.
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===Member types===
 
===Member types===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc hitem|Member type|Definition}}
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{{dsc hitem|Type|Definition}}
 
{{dsc inc|cpp/container/dsc container_type|flat_multiset}}
 
{{dsc inc|cpp/container/dsc container_type|flat_multiset}}
 
{{dsc inc|cpp/container/dsc key_type|flat_multiset}}
 
{{dsc inc|cpp/container/dsc key_type|flat_multiset}}
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===Member objects===
 
===Member objects===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc hitem|Member name|Definition}}
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{{dsc hitem|Member|Description}}
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{{dsc expos mem obj|private=yes|c|the underlying container of {{tt|container_type}}}}
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{{dsc expos mem obj|c|id=c|private=yes|spec={{tt|container_type}}|the adapted container}}
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{{dsc expos mem obj|private=yes|compare|the comparison function object of type {{tt|key_compare}}}}
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{{dsc expos mem obj|compare|id=compare|private=yes|spec={{tt|key_compare}}|the comparison function object}}
 
{{dsc end}}
 
{{dsc end}}
  
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{{dsc begin}}
 
{{dsc begin}}
 
{{dsc inc|cpp/container/dsc constructor|flat_multiset}}
 
{{dsc inc|cpp/container/dsc constructor|flat_multiset}}
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{{dsc inc|cpp/container/dsc destructor|flat_multiset}}<!--TODO: implicitly defined! -->
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{{dsc mem dtor|nolink=true|notes={{mark implicit}}|destroys every element of the container adaptor}}
 
{{dsc inc|cpp/container/dsc operator{{=}}|flat_multiset}}
 
{{dsc inc|cpp/container/dsc operator{{=}}|flat_multiset}}
  
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===Tags===
 
===Tags===
 
{{dsc begin}}
 
{{dsc begin}}
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{{dsc inc|cpp/container/dsc sorted_unique}}
 
 
{{dsc inc|cpp/container/dsc sorted_equivalent}}
 
{{dsc inc|cpp/container/dsc sorted_equivalent}}
 
{{dsc end}}
 
{{dsc end}}
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{{dsc begin}}
 
{{dsc begin}}
 
{{dsc inc|cpp/container/dsc flat_set}}
 
{{dsc inc|cpp/container/dsc flat_set}}
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{{dsc inc|cpp/container/dsc set}}
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{{dsc inc|cpp/container/dsc multiset}}
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{{dsc inc|cpp/container/dsc unordered_set}}
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{{dsc inc|cpp/container/dsc unordered_multiset}}
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{{dsc inc|cpp/container/dsc vector}}
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{{dsc end}}
 
{{dsc end}}
  
 
{{langlinks|cs|de|es|fr|it|ja|pl|pt|ru|zh}}
 
{{langlinks|cs|de|es|fr|it|ja|pl|pt|ru|zh}}
  
−
<!--TODO: N4950::24.6.11 says:
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<!--TODO: N4950::24.6.12 says:
 
TODO: add this to the "Exceptions" sections of appropriate member functions:
 
TODO: add this to the "Exceptions" sections of appropriate member functions:
 
6. If any member function in 24.6.12.2 exits via an exception, the invariant is restored.
 
6. If any member function in 24.6.12.2 exits via an exception, the invariant is restored.

Latest revision as of 14:53, 1 November 2024

 
C++
 
Containers library
 
std::flat_multiset
Member types
Member functions
Non-member functions
Helper classes
Tags
Deduction guides
 
Defined in header <flat_set>
template<

    class Key,
    class Compare = std::less<Key>,
    class KeyContainer = std::vector<Key>

> class flat_multiset;
 (since C++23)

The flat multiset is a container adaptor that gives the functionality of an associative container that stores a sorted set of objects of type Key. Unlike std::flat_set, multiple keys with equivalent values are allowed. Sorting is done using the key comparison function Compare.

The class template flat_multiset acts as a wrapper to the underlying sorted container passed as object of type KeyContainer.

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


std::flat_multiset meets the requirements of Container, ReversibleContainer, optional container requirements, and all requirements of AssociativeContainer (including logarithmic search complexity), except that:

  • requirements related to nodes are not applicable,
  • iterator invalidation requirements differ,
  • the complexity of insertion and erasure operations is linear.

A flat multiset supports most AssociativeContainer's operations that use equal keys.

Contents

[edit] Iterator invalidation

This section is incomplete

[edit] Template parameters

Key - The type of the stored elements. The program is ill-formed if Key is not the same type as KeyContainer::value_type.
Compare - A Compare type providing a strict weak ordering.
KeyContainer - The type of the underlying SequenceContainer to store the elements. The iterators of such container should satisfy LegacyRandomAccessIterator or model random_access_iterator.

The standard containers std::vector and std::deque satisfy these requirements.

[edit] Member types

Type Definition
container_type KeyContainer[edit]
key_type Key[edit]
value_type Key[edit]
key_compare Compare[edit]
value_compare Compare[edit]
reference value_type&[edit]
const_reference const value_type&[edit]
size_type typename KeyContainer::size_type[edit]
difference_type typename KeyContainer::difference_type[edit]
iterator implementation-defined LegacyRandomAccessIterator and random_access_iterator to value_type[edit]
const_iterator implementation-defined LegacyRandomAccessIterator and random_access_iterator to const value_type[edit]
reverse_iterator std::reverse_iterator<iterator>[edit]
const_reverse_iterator std::reverse_iterator<const_iterator>[edit]

[edit] Member objects

Member Description
container_type c (private) the adapted container
(exposition-only member object*)
key_compare compare (private) the comparison function object
(exposition-only member object*)

[edit] Member functions

 constructs the flat_multiset
(public member function) [edit]
(destructor)
(implicitly declared)
 destroys every element of the container adaptor
(public member function)
assigns values to the container adaptor
(public member function) [edit]
Iterators
returns an iterator to the beginning
(public member function) [edit]
returns an iterator to the end
(public member function) [edit]
returns a reverse iterator to the beginning
(public member function) [edit]
returns a reverse iterator to the end
(public member function) [edit]
Capacity
checks whether the container adaptor 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
constructs element in-place
(public member function) [edit]
constructs elements in-place using a hint
(public member function) [edit]
inserts elements
(public member function) [edit]
inserts a range of elements
(public member function) [edit]
extracts the underlying container
(public member function) [edit]
replaces the underlying container
(public member function) [edit]
erases elements
(public member function) [edit]
swaps the contents
(public member function) [edit]
clears the contents
(public member function) [edit]
Lookup
finds element with specific key
(public member function) [edit]
returns the number of elements matching specific key
(public member function) [edit]
checks if the container contains element with 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]
returns range of elements matching a specific 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

(C++23)
 lexicographically compares the values of two flat_multisets
(function template) [edit]
(C++23)
 specializes the std::swap algorithm
(function template) [edit]
(C++23)
 erases all elements satisfying specific criteria
(function template) [edit]

[edit] Helper classes

(C++23)
 specializes the std::uses_allocator type trait
(class template specialization) [edit]

[edit] Tags

(C++23)
 indicates that elements of a range are sorted (uniqueness is not required)
(tag)[edit]

[edit] Deduction guides

[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_flat_set 202207L (C++23) std::flat_set and std::flat_multiset

[edit] Example

This section is incomplete
Reason: no example

[edit] See also

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