Effects: Constructs a local variable start of type BidirectionalIterator and initializes it with the value of match.second.
If the iterator holds a zero-length match and start == end the operator sets *this to the end-of-sequence iterator and returns *this.
regex_search(start, end, match, *pregex, flags | regex_constants::match_not_null | regex_constants::match_continuous)
If the call returns true the operator returns *this. Otherwise the operator increments start and continues as if the most recent match was not a zero-length match.
If the most recent match was not a zero-length match, the operator sets flags to flags | regex_constants::match_prev_avail and calls regex_search(start, end, match, *pregex, flags). If the call returns false the iterator sets *this to the end-of-sequence iterator. The iterator then returns *this.
In all cases in which the call to regex_search returns true, match.prefix().first shall be equal to the previous value of match.second, and for each index i in the half-open range [0, match.size()) for which match[i].matched is true, match.position(i) shall return distance(begin, match[i].first).
[ Note: This means that match.position(i) gives the offset from the beginning of the target sequence, which is often not the same as the offset from the sequence passed in the call to regex_search. — end note ]
[ Note: This means that a compiler may call an implementation-specific search function, in which case a user-defined specialization of regex_search will not be called. — end note ]