If k does not match the key of any element in the container, the function inserts a new element with that key and returns a reference to its mapped value. Notice that this always increases the container size by one, even if no mapped value is assigned to the element (the element is constructed using its default constructor).
A similar member function, map::at, has the same behavior when an element with the key exists, but throws an exception when it does not.
A call to this function is equivalent to:
- Key value of the element whose mapped value is accessed.
Member type key_type is the type of the keys for the elements stored in the container, defined in map as an alias of its first template parameter (Key).
If an rvalue (second version), the key is moved instead of copied when a new element is inserted.
Return valueA reference to the mapped value of the element with a key value equivalent to k.
Member type mapped_type is the type of the mapped values in the container, defined in map as an alias of its second template parameter (T).