std::map::value_compare
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   class value_compare;  | 
||
std::map::value_compare is a function object that compares objects of type std::map::value_type (key-value pairs) by comparing of the first components of the pairs.
[edit] Member types
| Type | Definition | 
| result_type | bool | 
| first_argument_type | value_type | 
| second_argument_type | value_type | 
[edit] Protected member objects
| Name | Type | 
| comp | Compare | 
[edit] Member functions
|   constructs a new value_compare object  (protected member function)  | |
|    compares two values of type value_type  (public member function)  | |