Element access

at

value_type& at( const key_type& key );

const value_type& at( const key_type& key ) const;

Returns: a reference to item.second, where item is the element with the key equivalent to key.

Throws: std::out_of_range exception if the element with the key equivalent to key is not presented in the container.

operator[]

value_type& operator[]( const key_type& key );

If the element with the key equivalent to key is not presented in the container, inserts a new element constructed in-place from std::piecewise_construct, std::forward_as_tuple(key), std::tuple<>().

Requirements: the type value_type must meet the EmplaceConstructible requirements from the [container.requirements] ISO C++ Standard section.

Returns: a reference to item.second, where item is the element with the key equivalent to key.

---

value_type& operator[]( key_type&& key );

If the element with the key equivalent to key is not presented in the container, inserts a new element constructed in-place from std::piecewise_construct, std::forward_as_tuple(std::move(key)), std::tuple<>().

Requirements: the type value_type must meet the EmplaceConstructible requirements from the [container.requirements] ISO C++ Standard section.

Returns: a reference to item.second where item is the element with the key equivalent to key.