[#bsl-unordered_map-02b-2constructor-09b]
= xref:bsl.adoc[bsl]::xref:bsl/unordered_map-02b.adoc[unordered_map]::unordered_map
:relfileprefix: ../../
:mrdocs:

Create an empty unordered map, having a `max_load_factor` of 1.0, and then create a `value_type` object for each iterator in the range starting at the specified `first` iterator and ending immediately before the specified `last` iterator, by converting from the object referred to by each iterator. Insert into this unordered map each such object, ignoring those having a key that appears earlier in the sequence. Optionally specify a minimum `initialNumBuckets` indicating the minimum initial size of the array of buckets of this unordered map. If `initialNumBuckets` is 0 or not supplied, and `first` and `last` denote an empty range, a single empty bucket shall be supplied. The actual number of buckets the unordered_map is created with shall always be enough to accommodate the number of elements of the range without exceeding the `max_load_factor`. Optionally specify a `hashFunction` used to generate hash values associated with the `KEY‐VALUE` pairs contained in this unordered map. If `hashFunction` is not supplied, a default‐constructed object of the (template parameter) type `HASH` is used. Optionally specify a key‐equality functor `keyEqual` used to verify that two keys are equivalent. If `keyEqual` is not supplied, a default‐constructed object of the (template parameter) type `EQUAL` is used. Optionally specify a `basicAllocator` used to supply memory. If `basicAllocator` is not supplied, a default‐constructed object of the (template parameter) type `ALLOCATOR` is used. If `ALLOCATOR` type is `bsl::allocator` (the default), then `basicAllocator` shall be convertible to `bslma::Allocator *`. If the `ALLOCATOR` type is `bsl::allocator` and `basicAllocator` is not supplied, the currently installed default allocator is used to supply memory. The (template parameter) type `INPUT_ITERATOR` shall meet the requirements of an input iterator defined in the C++11 standard [24.2.3]providing access to values of a type convertible to `value_type`. The behavior is undefined unless `first` and `last` refer to a sequence of valid values where `first` is at a position at or before `last`. Note that more than `initialNumBuckets` buckets may be created in order to preserve the bucket allocation strategy of the hash‐table (but never fewer).

== Synopsis

Declared in `<bslstl_unorderedmap.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class INPUT_ITERATOR>
unordered_map(
    INPUT_ITERATOR first,
    INPUT_ITERATOR last,
    xref:bsl/unordered_map-02b/size_type.adoc[size_type] initialNumBuckets = 0,
    HASH const& hashFunction = HASH(),
    EQUAL const& keyEqual = EQUAL(),
    ALLOCATOR const& basicAllocator = ALLOCATOR());
----


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