Effects: Constructs an end-of-sequence iterator.

regex_iterator(BidirectionalIterator a, BidirectionalIterator b, const regex_type& re, regex_constants::match_flag_type m = regex_constants::match_default);

Effects: Initializes begin and end to a and b, respectively, sets pregex to addressof(re), sets flags to m, then calls regex_search(begin, end, match, *pregex, flags).

If this call returns false the constructor sets *this to the end-of-sequence iterator.