[#bsl-unordered_multimap-0b0]
= xref:bsl.adoc[bsl]::unordered&lowbar;multimap
:relfileprefix: ../
:mrdocs:

Unordered associative container mapping keys to values, allowing duplicates&period;

== Synopsis

Declared in `&lt;bslstl&lowbar;unorderedmultimap&period;h&gt;`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template&lt;
    class KEY,
    class VALUE,
    class HASH = xref:bsl/hash-06.adoc[bsl::hash&lt;KEY&gt;],
    class EQUAL = xref:bsl/equal_to-0d.adoc[bsl::equal&lowbar;to&lt;KEY&gt;],
    class ALLOCATOR = xref:bsl/allocator-0df.adoc[bsl::allocator&lt;bsl::pair&lt;KEY const, VALUE&gt;&gt;]&gt;
class unordered&lowbar;multimap;
----

== Description

This class template implements a value&hyphen;semantic container type holding a collection of (possibly equivalent) keys (of the template parameter type `KEY`), each mapped to their associated values (of another template parameter type `VALUE`)&period;

This class&colon; &ast; supports a complete set of _value&hyphen;semantic_ operations

* except for BDEX serialization &ast; is _exception&hyphen;neutral_ (agnostic except for the `at` method) &ast; is _alias&hyphen;safe_ &ast; is `const` _thread&hyphen;safe_ For terminology see &lcub;`bsldoc&lowbar;glossary`&rcub;&period;

== Type Aliases

[cols="1,4"]
|===
| Name| Description
| xref:bsl/unordered_multimap-0b0/allocator_type.adoc[`allocator&lowbar;type`] 
| This `typedef` is an alias for `allocator&lowbar;type`&period;
| xref:bsl/unordered_multimap-0b0/const_iterator.adoc[`const&lowbar;iterator`] 
| This `typedef` is an alias for `const&lowbar;iterator`&period;
| xref:bsl/unordered_multimap-0b0/const_local_iterator.adoc[`const&lowbar;local&lowbar;iterator`] 
| This `typedef` is an alias for `const&lowbar;local&lowbar;iterator`&period;
| xref:bsl/unordered_multimap-0b0/const_pointer.adoc[`const&lowbar;pointer`] 
| This `typedef` is an alias to `AllocatorTraits&colon;&colon;const&lowbar;pointer`&period;
| xref:bsl/unordered_multimap-0b0/const_reference.adoc[`const&lowbar;reference`] 
| This `typedef` is an alias for `const&lowbar;reference`&period;
| xref:bsl/unordered_multimap-0b0/difference_type.adoc[`difference&lowbar;type`] 
| This `typedef` is an alias for `difference&lowbar;type`&period;
| xref:bsl/unordered_multimap-0b0/hasher.adoc[`hasher`] 
| This `typedef` is an alias to the (template parameter) `HASH`&period;
| xref:bsl/unordered_multimap-0b0/iterator.adoc[`iterator`] 
| This `typedef` is an alias for `iterator`&period;
| xref:bsl/unordered_multimap-0b0/key_equal.adoc[`key&lowbar;equal`] 
| This `typedef` is an alias for `key&lowbar;equal`&period;
| xref:bsl/unordered_multimap-0b0/key_type.adoc[`key&lowbar;type`] 
| This `typedef` is an alias for `key&lowbar;type`&period;
| xref:bsl/unordered_multimap-0b0/local_iterator.adoc[`local&lowbar;iterator`] 
| This `typedef` is an alias for `local&lowbar;iterator`&period;
| xref:bsl/unordered_multimap-0b0/mapped_type.adoc[`mapped&lowbar;type`] 
| This `typedef` is an alias for `mapped&lowbar;type`&period;
| xref:bsl/unordered_multimap-0b0/pointer.adoc[`pointer`] 
| This `typedef` is an alias for `pointer`&period;
| xref:bsl/unordered_multimap-0b0/reference.adoc[`reference`] 
| This `typedef` is an alias to `value&lowbar;type&amp;`&period;
| xref:bsl/unordered_multimap-0b0/size_type.adoc[`size&lowbar;type`] 
| This `typedef` is an alias for `size&lowbar;type`&period;
| xref:bsl/unordered_multimap-0b0/value_type.adoc[`value&lowbar;type`] 
| This `typedef` is an alias to `bsl&colon;&colon;pair&lt;const KEY, VALUE&gt;`&period;
|===


== Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/unordered_multimap-0b0/2constructor-06.adoc[`unordered&lowbar;multimap`]         [.small]#[constructor]#
| Constructors
| xref:bsl/unordered_multimap-0b0/2destructor.adoc[`&#126;unordered&lowbar;multimap`] [.small]#[destructor]#
| Destroy this object&period;
| xref:bsl/unordered_multimap-0b0/operator_assign-0b.adoc[`operator&equals;`] 
| Assignment operators
| xref:bsl/unordered_multimap-0b0/begin-096.adoc[`begin`] 
| `begin` overloads
| xref:bsl/unordered_multimap-0b0/bucket-00d.adoc[`bucket`] 
| `bucket` overloads
| xref:bsl/unordered_multimap-0b0/bucket_count.adoc[`bucket&lowbar;count`] 
| Return the number of buckets in the array of buckets maintained by this unordered multimap&period;
| xref:bsl/unordered_multimap-0b0/bucket_size.adoc[`bucket&lowbar;size`] 
| Return the number of elements in the bucket at `index`&period;
| xref:bsl/unordered_multimap-0b0/cbegin-01.adoc[`cbegin`] 
| `cbegin` overloads
| xref:bsl/unordered_multimap-0b0/cend-03.adoc[`cend`] 
| `cend` overloads
| xref:bsl/unordered_multimap-0b0/clear.adoc[`clear`] 
| Remove all entries from this unordered multimap&period; Note that this object will be empty after this call, but allocated memory may be retained for future use&period;
| xref:bsl/unordered_multimap-0b0/contains-0e.adoc[`contains`] 
| Return `true` if this container has an element with key equivalent to `key`&period;
| xref:bsl/unordered_multimap-0b0/count-09.adoc[`count`] 
| Return the number of elements with a key equivalent to `key`&period;
| xref:bsl/unordered_multimap-0b0/emplace.adoc[`emplace`] 
| Emplace a newly constructed element into this container&period;
| xref:bsl/unordered_multimap-0b0/emplace_hint.adoc[`emplace&lowbar;hint`] 
| Emplace a newly constructed element near `hint`&period;
| xref:bsl/unordered_multimap-0b0/empty.adoc[`empty`] 
| Return `true` if this unordered multimap contains no elements, and `false` otherwise&period;
| xref:bsl/unordered_multimap-0b0/end-0d.adoc[`end`] 
| `end` overloads
| xref:bsl/unordered_multimap-0b0/equal_range-0c.adoc[`equal&lowbar;range`] 
| Return an iterator pair covering elements with key equivalent to `key`&period;
| xref:bsl/unordered_multimap-0b0/erase-0b5.adoc[`erase`] 
| `erase` overloads
| xref:bsl/unordered_multimap-0b0/find-00.adoc[`find`] 
| Return an iterator to the first element with key equivalent to `key`&period;
| xref:bsl/unordered_multimap-0b0/get_allocator.adoc[`get&lowbar;allocator`] 
| Return (a copy of) the allocator used for memory allocation by this unordered multimap&period;
| xref:bsl/unordered_multimap-0b0/hash_function.adoc[`hash&lowbar;function`] 
| Return (a copy of) the hash unary functor used by this unordered multimap to generate a hash value (of type `size&lowbar;type`) for a `key&lowbar;type` object&period;
| xref:bsl/unordered_multimap-0b0/insert-0a.adoc[`insert`] 
| `insert` overloads
| xref:bsl/unordered_multimap-0b0/insert_range.adoc[`insert&lowbar;range`] 
| Insert each element from the specified `range`&period;
| xref:bsl/unordered_multimap-0b0/key_eq.adoc[`key&lowbar;eq`] 
| Return (a copy of) the key&hyphen;equivalence binary functor that returns `true` if the value of two `key&lowbar;type` objects are equivalent, and `false` otherwise&period;
| xref:bsl/unordered_multimap-0b0/load_factor.adoc[`load&lowbar;factor`] 
| Return the current load factor of this container&period;
| xref:bsl/unordered_multimap-0b0/max_bucket_count.adoc[`max&lowbar;bucket&lowbar;count`] 
| Return a theoretical upper bound on the number of buckets&period;
| xref:bsl/unordered_multimap-0b0/max_load_factor-0f.adoc[`max&lowbar;load&lowbar;factor`] 
| `max&lowbar;load&lowbar;factor` overloads
| xref:bsl/unordered_multimap-0b0/max_size.adoc[`max&lowbar;size`] 
| Return a theoretical upper bound on the number of elements&period;
| xref:bsl/unordered_multimap-0b0/rehash.adoc[`rehash`] 
| Rehash this container to have at least `numBuckets` buckets&period;
| xref:bsl/unordered_multimap-0b0/reserve.adoc[`reserve`] 
| Reserve capacity for at least `numElements` without rehashing&period;
| xref:bsl/unordered_multimap-0b0/size.adoc[`size`] 
| Return the number of elements in this unordered multimap&period;
| xref:bsl/unordered_multimap-0b0/swap.adoc[`swap`] 
| Exchange the contents of this object with those of `other`&period;
|===


== Deduction Guides

[cols="1,4"]
|===
| Name| Description
| xref:bsl/unordered_multimap-0d8.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE&gt;`] 
| Deduce template arguments from an initializer&hyphen;list constructor&period;
| xref:bsl/unordered_multimap-02.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE&gt;`] 
| Deduce template arguments from an initializer&hyphen;list constructor&period;
| xref:bsl/unordered_multimap-048a.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE&gt;`] 
| Deduce template arguments from an initializer&hyphen;list constructor&period;
| xref:bsl/unordered_multimap-07.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE&gt;`] 
| Deduce template arguments from iterators with size and `bslma` allocator&period;
| xref:bsl/unordered_multimap-044.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, HASH&gt;`] 
| Deduce template arguments from an initializer&hyphen;list constructor&period;
| xref:bsl/unordered_multimap-08f.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, HASH&gt;`] 
| Deduce template arguments from a constructor taking a `bslma` allocator&period;
| xref:bsl/unordered_multimap-00.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, HASH, EQUAL&gt;`] 
| Deduce template arguments from an initializer&hyphen;list constructor&period;
| xref:bsl/unordered_multimap-06.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, HASH, EQUAL&gt;`] 
| Deduce template arguments from a constructor taking a `bslma` allocator&period;
| xref:bsl/unordered_multimap-0e.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, HASH, EQUAL, ALLOCATOR&gt;`] 
| Deduce template arguments from an initializer&hyphen;list constructor&period;
| xref:bsl/unordered_multimap-0d6.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, HASH, EQUAL, ALLOCATOR&gt;`] 
| Deduce template arguments for an `unordered&lowbar;multimap` constructor&period;
| xref:bsl/unordered_multimap-048e.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, HASH, bsl::equal&lowbar;to&lt;KEY&gt;, ALLOCATOR&gt;`] 
| Deduce template arguments from an initializer&hyphen;list constructor&period;
| xref:bsl/unordered_multimap-084.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, HASH, bsl::equal&lowbar;to&lt;KEY&gt;, ALLOCATOR&gt;`] 
| Deduce template arguments for an `unordered&lowbar;multimap` constructor&period;
| xref:bsl/unordered_multimap-04c.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, bsl::hash&lt;KEY&gt;, bsl::equal&lowbar;to&lt;KEY&gt;, ALLOCATOR&gt;`] 
| Deduce template arguments from an initializer&hyphen;list constructor&period;
| xref:bsl/unordered_multimap-0b8.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, bsl::hash&lt;KEY&gt;, bsl::equal&lowbar;to&lt;KEY&gt;, ALLOCATOR&gt;`] 
| Deduce template arguments from an initializer&hyphen;list constructor&period;
| xref:bsl/unordered_multimap-0b6.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, bsl::hash&lt;KEY&gt;, bsl::equal&lowbar;to&lt;KEY&gt;, ALLOCATOR&gt;`] 
| Deduce template arguments for an `unordered&lowbar;multimap` constructor&period;
| xref:bsl/unordered_multimap-04e.adoc[`unordered&lowbar;multimap&lt;KEY, VALUE, bsl::hash&lt;KEY&gt;, bsl::equal&lowbar;to&lt;KEY&gt;, ALLOCATOR&gt;`] 
| Deduce template arguments for an `unordered&lowbar;multimap` constructor&period;
|===


== Friends

[cols="1,4"]
|===
| Name| Description
| `xref:bsl/operator_eq-068.adoc[bsl::operator&equals;&equals;]`
| Return `true` if `lhs` and `rhs` have the same value&period;
|===

== Non-Member Functions

[cols="1,4"]
|===
| Name| Description
| xref:bsl/erase_if-0aa.adoc[`erase&lowbar;if`]
| Erase every element of `m` that satisfies `predicate`&period;
| xref:bsl/operator_eq-08a.adoc[`operator&equals;&equals;`]
| Return `true` if `lhs` and `rhs` have the same value&period;
| xref:bsl/swap-08c.adoc[`swap`]
| Exchange the value of `a` with that of `b`&period;
|===


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