Difference between revisions of "cpp/container/multimap"
Andreas Krug (Talk | contribs) m (-line) |
Andreas Krug (Talk | contribs) m (fmt) |
||
| Line 13: | Line 13: | ||
{{dcl|num=2|since=c++17|1= | {{dcl|num=2|since=c++17|1= | ||
namespace pmr { | namespace pmr { | ||
| − | template< | + | template< |
| − | + | class Key, | |
| − | + | class T, | |
| − | + | class Compare = std::less<Key> | |
| − | > using multimap = | + | > using multimap = std::multimap<Key, T, Compare, |
| − | + | std::pmr::polymorphic_allocator<std::pair<const Key, T>>>; | |
| − | + | ||
} | } | ||
}} | }} | ||
Revision as of 01:37, 30 October 2023
| Defined in header <map>
|
||
| template< class Key, |
(1) | |
| namespace pmr { template< |
(2) | (since C++17) |
std::multimap is an associative container that contains a sorted list of key-value pairs, while permitting multiple entries with the same key. Sorting is done according to the comparison function Compare, applied to the keys. Search, insertion, and removal operations have logarithmic complexity.
|
The order of the key-value pairs whose keys compare equivalent is the order of insertion and does not change. |
(since C++11) |
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).
std::multimap meets the requirements of Container, AllocatorAwareContainer, AssociativeContainer and ReversibleContainer.
Contents |
Template parameters
| This section is incomplete Reason: Add descriptions of the template parameters. |
Member types
| Member type | Definition | ||||
key_type
|
Key
| ||||
mapped_type
|
T
| ||||
value_type
|
std::pair<const Key, T> | ||||
size_type
|
Unsigned integer type (usually std::size_t) | ||||
difference_type
|
Signed integer type (usually std::ptrdiff_t) | ||||
key_compare
|
Compare
| ||||
allocator_type
|
Allocator
| ||||
reference
|
value_type& | ||||
const_reference
|
const value_type& | ||||
pointer
|
| ||||
const_pointer
|
| ||||
iterator
|
LegacyBidirectionalIterator to value_type
| ||||
const_iterator
|
LegacyBidirectionalIterator to const value_type | ||||
reverse_iterator
|
std::reverse_iterator<iterator> | ||||
const_reverse_iterator
|
std::reverse_iterator<const_iterator> | ||||
node_type (since C++17)
|
a specialization of node handle representing a container node |
Member classes
compares objects of type value_type (class) |
Member functions
constructs the multimap (public member function) | |
destructs the multimap (public member function) | |
| assigns values to the container (public member function) | |
| returns the associated allocator (public member function) | |
Iterators | |
| (C++11) |
returns an iterator to the beginning (public member function) |
| (C++11) |
returns an iterator to the end (public member function) |
| (C++11) |
returns a reverse iterator to the beginning (public member function) |
| (C++11) |
returns a reverse iterator to the end (public member function) |
Capacity | |
| checks whether the container is empty (public member function) | |
| returns the number of elements (public member function) | |
| returns the maximum possible number of elements (public member function) | |
Modifiers | |
| clears the contents (public member function) | |
| inserts elements or nodes(since C++17) (public member function) | |
| (C++23) |
inserts a range of elements (public member function) |
| (C++11) |
constructs element in-place (public member function) |
| (C++11) |
constructs elements in-place using a hint (public member function) |
| erases elements (public member function) | |
| swaps the contents (public member function) | |
| (C++17) |
extracts nodes from the container (public member function) |
| (C++17) |
splices nodes from another container (public member function) |
Lookup | |
| returns the number of elements matching specific key (public member function) | |
| finds element with specific key (public member function) | |
| (C++20) |
checks if the container contains element with specific key (public member function) |
| returns range of elements matching a specific key (public member function) | |
| returns an iterator to the first element not less than the given key (public member function) | |
| returns an iterator to the first element greater than the given key (public member function) | |
Observers | |
| returns the function that compares keys (public member function) | |
returns the function that compares keys in objects of type value_type (public member function) | |
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 multimaps (function template) |
| specializes the std::swap algorithm (function template) | |
| (C++20) |
erases all elements satisfying specific criteria (function template) |
Deduction guides |
(since C++17) |
Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_containers_ranges |
202202L | (C++23) | Ranges construction and insertion for containers |
Example
| This section is incomplete Reason: no example |
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 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 tobe CopyConstructible |
