[#bsl-unordered_set-09-emplace]
= xref:bsl.adoc[bsl]::xref:bsl/unordered_set-09.adoc[unordered_set<Attribute, AttributeHash>]::emplace
:relfileprefix: ../../
:mrdocs:

Insert into this unordered set a newly created `value_type` object, constructed by forwarding `get_allocator()` (if required) and the specified (variable number of) `arguments` to the corresponding constructor of `value_type`, if a key equivalent to such a value does not already exist in this set; otherwise, this method has no effect (other than possibly creating a temporary `value_type` object). Return a pair whose `first` member is an iterator referring to the (possibly newly created and inserted) object in this set whose value is equivalent to that of an object constructed from `arguments`, and whose `second` member is `true` if a new value was inserted, and `false` if an equivalent key was already present. This method requires that the (template parameter) type `KEY` be `emplace‐constructible` into this set from `arguments` (see {Requirements on `KEY`}).

== Synopsis

Declared in `<bslstl_unorderedset.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class... Args>
xref:bsl/pair-0b.adoc[pair<iterator, bool>]
emplace(Args&&... arguments);
----


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