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std::regex_token_iterator(3) C++ Standard Libary std::regex_token_iterator(3) NAME std::regex_token_iterator - std::regex_token_iterator Synopsis Defined in header <regex> template< class BidirIt, class CharT = typename std::iterator_traits<BidirIt>::value_type, (since C++11) class Traits = std::regex_traits<CharT> > class regex_token_iterator std::regex_token_iterator is a read-only LegacyForwardIterator that accesses the individual sub-matches of every match of a regular expression within the underlying character sequence. It can also be used to access the parts of the sequence that were not matched by the given regular expression (e.g. as a tok- enizer). On construction, it constructs an std::regex_iterator and on every increment it steps through the requested sub-matches from the current match_re- sults, incrementing the underlying regex_iterator when incrementing away from the last submatch. The default-constructed std::regex_token_iterator is the end-of-se- quence iterator. When a valid std::regex_token_iterator is incremented after reaching the last submatch of the last match, it becomes equal to the end-of-sequence iterator. Dereferencing or incrementing it further invokes undefined behavior. Just before becoming the end-of-sequence iterator, a std::regex_to- ken_iterator may become a suffix iterator, if the index -1 (non-matched fragment) ap- pears in the list of the requested submatch indexes. Such iterator, if dereferenced, returns a match_results corresponding to the sequence of characters between the last match and the end of sequence. A typical implementation of std::regex_token_iterator holds the un- derlying std::regex_iterator, a container (e.g. std::vector<int>) of the re- quested submatch indexes, the internal counter equal to the index of the submatch, a pointer to std::sub_match, pointing at the current submatch of the current match, and a std::match_results object containing the last non-matched character sequence (used in tokenizer mode). Type requirements - BidirIt must meet the requirements of LegacyBidirectionalIterator. Specializations Several specializations for common character sequence types are de- fined: Defined in header <regex> Type Definition cregex_token_iterator regex_token_iterator<const char*> wcregex_token_iterator regex_token_iterator<const wchar_t*> sregex_token_iterator regex_token_iterator<std::string::const_iter- ator> wsregex_token_iterator regex_token_iterator<std::wstring::const_it- erator> Member types Member type Definition value_type std::sub_match<BidirIt> difference_type std::ptrdiff_t pointer const value_type* reference const value_type& iterator_category std::forward_iterator_tag regex_type basic_regex<CharT, Traits> Member functions constructor constructs a new regex_token_iterator (public member function) destructor destructs a regex_token_iterator, including the cached value (implicitly declared) (public member function) operator= assigns contents (public member function) operator== compares two regex_token_iterators operator!= (public member function) (removed in C++20) operator* accesses current submatch operator-> (public member function) operator++ advances the iterator to the next submatch operator++(int) (public member function) Notes It is the programmer's responsibility to ensure that the std::ba- sic_regex object passed to the iterator's constructor outlives the iterator. Because the iterator stores a std::regex_iterator which stores a pointer to the regex, incrementing the iterator after the regex was destroyed results in undefined behav- ior. Example // Run this code #include <fstream> #include <iostream> #include <algorithm> #include <iterator> #include <regex> int main() { // Tokenization (non-matched fragments) // Note that regex is matched only two times; when the third value is obtained // the iterator is a suffix iterator. const std::string text = "Quick brown fox."; const std::regex ws_re("\\s+"); // whitespace std::copy( std::sregex_token_iterator(text.begin(), text.end(), ws_re, -1), std::sregex_token_iterator(), std::ostream_iterator<std::string>(std::cout, "\n")); std::cout << '\n'; // Iterating the first submatches const std::string html = R"(<p><a href="http://google.com">google</a> )" R"(< a HREF ="http://cpprefer- ence.com">cppreference</a>\n</p>)"; const std::regex url_re(R"!!(<\s*A\s+[^>]*href\s*=\s*"([^"]*)")!!", std::regex::icase); std::copy( std::sregex_token_iterator(html.begin(), html.end(), url_re, 1), std::sregex_token_iterator(), std::ostream_iterator<std::string>(std::cout, "\n")); } Output: Quick brown fox. http://google.com http://cppreference.com http://cppreference.com 2022.07.31 std::regex_token_iterator(3)
NAME | Synopsis | Type requirements | Specializations | Member types | Member functions | Notes | Example | Output:
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