Return a reference providing modifiable access to the mapped-value associated with a key that is equivalent to the specified key, if such an entry exists; otherwise, throw a std::out_of_range exception. Note that this method may also throw a different kind of exception if the (user-supplied) comparator throws.
Declared in <bslstl_unorderedmap.h>
template<class LOOKUP_KEY>
add_lvalue_reference<VALUE>::type
at(LOOKUP_KEY const& key)
requires BloombergLP::bslmf::IsTransparentPredicate<HASH, LOOKUP_KEY>::value
&& BloombergLP::bslmf::IsTransparentPredicate<EQUAL,LOOKUP_KEY>::value;Note: implemented inline due to Sun CC compilation error