[#BloombergLP-bdlc-FlatHashSet-insert-0e3]
= xref:BloombergLP.adoc[BloombergLP]::xref:BloombergLP/bdlc.adoc[bdlc]::xref:BloombergLP/bdlc/FlatHashSet.adoc[FlatHashSet]::insert
:relfileprefix: ../../../
:mrdocs:

Insert the specified `key` into this set if a key equivalent to `k` does not already exist in this set; otherwise, this method has no effect. Return a pair containing an `iterator` referring to the newly inserted element and `true` if a element was inserted. Return a pair containing an `iterator` to an existing element and `false` if the value already existed in the set.

== Synopsis

Declared in `<bdlc_flathashset.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
template<class LOOKUP_KEY>
xref:bsl/pair-0b.adoc[bsl::pair<iterator, bool>]
insert(LOOKUP_KEY&& key)
requires BloombergLP::bslmf::IsTransparentPredicate<HASH, LOOKUP_KEY>::value
         && BloombergLP::bslmf::IsTransparentPredicate<EQUAL,LOOKUP_KEY>::value;
----


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