Return a reference providing modifiable access to the mapped-value associated with a key that is equivalent with the specified key; if this map does not already contain a value_type object having an equivalent key, first insert a new value_type object having the move-inserted key and a default-constructed VALUE object, and return a reference to the newly mapped (default) value. This method requires that the (template parameter) type KEY be move-insertable into this map and the (template parameter) type VALUE be default-insertable into this map (see {Requirements on KEY and VALUE}).
Declared in <bslstl_map.h>
template<class LOOKUP_KEY>
add_lvalue_reference<VALUE>::type
operator[](LOOKUP_KEY&& key)
requires BloombergLP::bslmf::IsTransparentPredicate<COMPARATOR,
LOOKUP_KEY>::value;