[#bsl-multiset-03]
= xref:bsl.adoc[bsl]::multiset
:relfileprefix: ../
:mrdocs:

This class template implements a value‐semantic container type holding an ordered sequence of possibly duplicate keys (of the template parameter type, `KEY`).

== Synopsis

Declared in `<bslstl_multiset.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<
    class KEY,
    class COMPARATOR = std::less<KEY>,
    class ALLOCATOR = xref:bsl/allocator-0df.adoc[bsl::allocator<KEY>]>
class multiset;
----

== Description

This class: * supports a complete set of _value‐semantic_ operations

* except for BDEX serialization * is _exception‐neutral_ (agnostic except for the `at` method) * is _alias‐safe_ * is `const` _thread‐safe_ For terminology see {`bsldoc_glossary`}.

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:bsl/multiset-03/allocator_type.adoc[`allocator_type`] 
| This `typedef` is an alias to the (template parameter) `ALLOCATOR`.
| xref:bsl/multiset-03/const_iterator.adoc[`const_iterator`] 
| This `typedef` is an alias to `iterator`.
| xref:bsl/multiset-03/const_pointer.adoc[`const_pointer`] 
| This `typedef` is an alias to the allocator const‐pointer type.
| xref:bsl/multiset-03/const_reference.adoc[`const_reference`] 
| This `typedef` is an alias for `const_reference`.
| xref:bsl/multiset-03/const_reverse_iterator.adoc[`const_reverse_iterator`] 
| This `typedef` is an alias to the const reverse iterator type.
| xref:bsl/multiset-03/difference_type.adoc[`difference_type`] 
| This `typedef` is an alias to the allocator difference type.
| xref:bsl/multiset-03/iterator.adoc[`iterator`] 
| This `typedef` is an alias to the red‐black tree iterator type.
| xref:bsl/multiset-03/key_compare.adoc[`key_compare`] 
| This `typedef` is an alias to the (template parameter) `COMPARATOR`.
| xref:bsl/multiset-03/key_type.adoc[`key_type`] 
| This `typedef` is an alias to the (template parameter) `KEY` type.
| xref:bsl/multiset-03/pointer.adoc[`pointer`] 
| This `typedef` is an alias to the allocator pointer type.
| xref:bsl/multiset-03/reference.adoc[`reference`] 
| This `typedef` is an alias to `value_type&`.
| xref:bsl/multiset-03/reverse_iterator.adoc[`reverse_iterator`] 
| This `typedef` is an alias to the reverse iterator type.
| xref:bsl/multiset-03/size_type.adoc[`size_type`] 
| This `typedef` is an alias to the allocator size type.
| xref:bsl/multiset-03/value_compare.adoc[`value_compare`] 
| This `typedef` is an alias to `key_compare`.
| xref:bsl/multiset-03/value_type.adoc[`value_type`] 
| This `typedef` is an alias to `key_type`.
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/multiset-03/2constructor-05.adoc[`multiset`]         [.small]#[constructor]#
| Constructors
| xref:bsl/multiset-03/2destructor.adoc[`~multiset`] [.small]#[destructor]#
| Destroy this object.
| xref:bsl/multiset-03/operator_assign-09.adoc[`operator=`] 
| Assignment operators
| xref:bsl/multiset-03/begin-00.adoc[`begin`] 
| `begin` overloads
| xref:bsl/multiset-03/cbegin.adoc[`cbegin`] 
| Return a const iterator to the first element, or `cend` if empty.
| xref:bsl/multiset-03/cend.adoc[`cend`] 
| Return an iterator providing non‐modifiable access to the past‐the‐end element in the ordered sequence of `value_type` objects maintained by this multiset.
| xref:bsl/multiset-03/clear.adoc[`clear`] 
| Remove all entries from this multiset. Note that the multiset is empty after this call, but allocated memory may be retained for future use.
| xref:bsl/multiset-03/contains-0b.adoc[`contains`] 
| Return whether this multiset contains an element equivalent to `key`.
| xref:bsl/multiset-03/count-064.adoc[`count`] 
| Return the number of elements equivalent to `key`.
| xref:bsl/multiset-03/crbegin.adoc[`crbegin`] 
| Return a const reverse iterator to the last element, or `crend`.
| xref:bsl/multiset-03/crend.adoc[`crend`] 
| Return a const reverse iterator to prior‐to‐beginning.
| xref:bsl/multiset-03/emplace.adoc[`emplace`] 
| Emplace a newly constructed element into this multiset.
| xref:bsl/multiset-03/emplace_hint.adoc[`emplace_hint`] 
| Emplace a newly constructed element near `hint`.
| xref:bsl/multiset-03/empty.adoc[`empty`] 
| Return `true` if this multiset contains no elements, and `false` otherwise.
| xref:bsl/multiset-03/end-05.adoc[`end`] 
| `end` overloads
| xref:bsl/multiset-03/equal_range-00.adoc[`equal_range`] 
| `equal_range` overloads
| xref:bsl/multiset-03/erase-0f.adoc[`erase`] 
| `erase` overloads
| xref:bsl/multiset-03/find-0b.adoc[`find`] 
| `find` overloads
| xref:bsl/multiset-03/get_allocator.adoc[`get_allocator`] 
| Return (a copy of) the allocator used for memory allocation by this multiset.
| xref:bsl/multiset-03/insert-07.adoc[`insert`] 
| `insert` overloads
| xref:bsl/multiset-03/insert_range.adoc[`insert_range`] 
| Insert each element from the specified `range`.
| xref:bsl/multiset-03/key_comp.adoc[`key_comp`] 
| Return the key‐comparison functor used by this multiset.
| xref:bsl/multiset-03/lower_bound-04.adoc[`lower_bound`] 
| `lower_bound` overloads
| xref:bsl/multiset-03/max_size.adoc[`max_size`] 
| Return a theoretical upper bound on this multiset's size.
| xref:bsl/multiset-03/rbegin-01.adoc[`rbegin`] 
| `rbegin` overloads
| xref:bsl/multiset-03/rend-0f.adoc[`rend`] 
| `rend` overloads
| xref:bsl/multiset-03/size.adoc[`size`] 
| Return the number of elements in this multiset.
| xref:bsl/multiset-03/swap.adoc[`swap`] 
| Exchange the value and comparator with `other`.
| xref:bsl/multiset-03/upper_bound-0e.adoc[`upper_bound`] 
| `upper_bound` overloads
| xref:bsl/multiset-03/value_comp.adoc[`value_comp`] 
| Return a functor for comparing two `value_type` objects.
|===


== Deduction Guides

[cols="1,4"]
|===
| Name| Description
| xref:bsl/multiset-02.adoc[`multiset<KEY>`] 
| Deduce `KEY` from an initializer list with `ALLOC *`.
| xref:bsl/multiset-06a.adoc[`multiset<KEY>`] 
| Deduce `KEY` from iterator construction with `ALLOC *`.
| xref:bsl/multiset-005.adoc[`multiset<KEY, COMPARATOR>`] 
| Deduce `KEY` and `COMPARATOR` from an initializer list with `ALLOC *`.
| xref:bsl/multiset-0a.adoc[`multiset<KEY, COMPARATOR>`] 
| Deduce `KEY` and `COMPARATOR` from iterator construction with `ALLOC *`.
| xref:bsl/multiset-05.adoc[`multiset<KEY, COMPARATOR, ALLOCATOR>`] 
| Deduce `KEY`, `COMPARATOR`, and `ALLOCATOR` from an initializer list.
| xref:bsl/multiset-060.adoc[`multiset<KEY, COMPARATOR, ALLOCATOR>`] 
| Deduce `KEY`, `COMPARATOR`, and `ALLOCATOR` from iterator construction.
| xref:bsl/multiset-00e.adoc[`multiset<KEY, std::less<KEY>, ALLOCATOR>`] 
| Deduce `KEY` and `ALLOCATOR` from an initializer‐list constructor.
| xref:bsl/multiset-0f.adoc[`multiset<KEY, std::less<KEY>, ALLOCATOR>`] 
| Deduce `KEY` and `ALLOCATOR` from iterator‐pair construction.
|===


== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/erase_if-030.adoc[`erase_if`]
| Erase all elements in `ms` that satisfy `predicate`.
| xref:bsl/operator_3way-0ff.adoc[`operator<=>`]
| Return the lexicographic three‐way comparison of `lhs` and `rhs`.
| xref:bsl/operator_eq-0a8.adoc[`operator==`]
| Return `true` if `lhs` and `rhs` have the same value.
| xref:bsl/swap-001.adoc[`swap`]
| Exchange the values of the specified `a` and `b` multisets.
|===


[.small]#Created with https://www.mrdocs.com[MrDocs]#