std::match_results::begin, std::match_results::cbegin
From cppreference.com
                    
                                        
                    < cpp | regex | match results
                    
                                                            
                    |   iterator begin(); 
 | 
(since C++11) | |
|   const_iterator begin() const; 
 | 
(since C++11) | |
|   const_iterator cbegin() const; 
 | 
(since C++11) | |
Returns an iterator to the beginning of the list of sub-matches. If match was successful, the iterator will point to the entire matched expression.
Contents | 
[edit] Parameters
(none)
[edit] Return value
Iterator to the first sub-match.
[edit] Exceptions
[edit] Complexity
Constant
[edit] See also
|    returns iterator to the end of the list of sub-matches  (public member function)  | 
|