Return the number of elements equivalent to the specified key.
Declared in <bdlc_flathashset.h>
template<class LOOKUP_KEY>
std::size_t
count(LOOKUP_KEY const& key) const
requires BloombergLP::bslmf::IsTransparentPredicate<HASH, LOOKUP_KEY>::value
&& BloombergLP::bslmf::IsTransparentPredicate<EQUAL,LOOKUP_KEY>::value;The behavior is undefined unless key is equivalent to at most one element in this unordered set. Note that since an unordered set maintains unique keys, the returned value will be either 0 or 1.
1 if key is present, and 0 otherwise
| Name | Description |
|---|---|
| key | key to count |