Multiple-key set
Multisets are associative containers with the same properties as set containers, but allowing for multiple keys with equal values.
In their implementation in the C++ Standard Template Library, multiset containers take the same three template parameters as set containers:
template < class Key, class Compare = less<Key>,
class Allocator = allocator<Key> > class set;
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Where the template parameters have the following meanings:
- Key: Key type: type of the elements contained in the container. Each elements in a multiset is also its key.
- Compare: Comparison class: A class that takes two arguments of the same type as the container elements and returns a bool. The expression comp(a,b), where comp is an object of this class and a and b are elements of the container, shall return true if a is to be placed at an earlier position than b in a strict weak ordering operation. This can either be a class implementing a function call operator or a pointer to a function (see constructor for an example). This defaults to less<Key>, which returns the same as applying the less-than operator (a<b).
The multiset object uses this expression to determine the position of the elements in the container. All elements in a multiset container are ordered following this rule at all times.
- Allocator: Type of the allocator object used to define the storage allocation model. By default, the allocator class template for type Key is used, which defines the simplest memory allocation model and is value-independent.
In the reference for the
multiset member functions, these same names (
Key,
Compare and
Allocator) are assumed for the template parameters.
The multiset class template is defined in header <set>.
Member functions
| operator= | Copy container content (public member function) |
Iterators:
| begin | Return iterator to beginning (public member function) |
| end | Return iterator to end (public member function) |
| rbegin | Return reverse iterator to reverse beginning (public member function) |
| rend | Return reverse iterator to reverse end (public member function) |
Capacity:
| empty | Test whether container is empty (public member function) |
| size | Return container size (public member function) |
| max_size | Return maximum size (public member function) |
Modifiers:
| insert | Insert element (public member function) |
| erase | Erase elements (public member function) |
| swap | Swap content (public member function) |
| clear | Clear content (public member function) |
Observers:
| key_comp | Return comparison object (public member function) |
| value_comp | Return comparison object (public member function) |
Operations:
| find | Get iterator to element (public member function) |
| count | Count elements with a specific key (public member function) |
| lower_bound | Return iterator to lower bound (public member function) |
| upper_bound | Return iterator to upper bound (public member function) |
| equal_range | Get range of equal elements (public member function) |
Allocator:
Member types
of
template <class Key, class Compare=less<Key>, class Allocator=allocator<Key> > class multiset;
| member type | definition |
|---|
| key_type | Key |
| value_type | Key |
| key_compare | Compare |
| value_compare | Compare |
| allocator_type | Allocator |
| reference | Allocator::reference |
| const_reference | Allocator::const_reference |
| iterator | Bidirectional iterator |
| const_iterator | Constant bidirectional iterator |
| size_type | Unsigned integral type (usually same as size_t) |
| difference_type | Signed integral type (usually same as ptrdiff_t) |
| pointer | Allocator::pointer |
| const_pointer | Allocator::const_pointer |
| reverse_iterator | reverse_iterator<iterator> |
| const_reverse_iterator | reverse_iterator<const_iterator> |
