std::regex_token_iterator<BidirIt,CharT,Traits>::regex_token_iterator
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                    < cpp | regex | regex token iterator
                    
                                                            
                    Constructs a new regex_token_iterator:
1) Default constructor. Constructs the end-of-sequence iterator.
2-5) First, copies the list of the requested submatch out of the 
submatches or submatch argument into the member list stored in the iterator and constructs the member std::regex_iterator by passing a, b, re, and m to its four-argument constructor (that constructor performs the initial call to std::regex_search) and sets the internal counter of submatches to zero.
-  If, after construction, the member regex_iteratoris not an end-of-sequence iterator, sets the member pointer to the address of the current std::sub_match.
-  Otherwise (if the member regex_iteratoris an end-of-sequence iterator), but the value -1 is one of the values insubmatches/submatch, turns*thisinto a suffix iterator pointing at the range[a,b)(the entire string is the non-matched suffix)
-  Otherwise (if -1 is not in the list of submatches), turns *thisinto the end-of-sequence iterator.
The behavior is undefined if any value in submatches is less than -1.
6) Copy constructor: performs member-wise copy (including making a copy of the member 
regex_iterator and the member pointer to current sub_match).7-10) The overloads 2-5 are prohibited from being called with a temporary regex since otherwise the returned iterator would be immediately invalidated
Parameters
| a | - | LegacyBidirectionalIterator to the beginning of the target character sequence | 
| b | - | LegacyBidirectionalIterator to the end of the target character sequence | 
| re | - | regular expression used to search the target character sequence | 
| submatch | - | the index of the submatch that should be returned. "0" represents the entire match, and "-1" represents the parts that are not matched (e.g, the stuff between matches). | 
| submatches | - | the sequence of submatch indices that should be iterated over within each match, may include the special value -1 for the non-matched fragments | 
| m | - | flags that govern the behavior of re | 
Example
| This section is incomplete Reason: no example |