std::regex_iterator
template< class BidirIt, |
(since C++11) | |
std::regex_iterator
is a read-only ForwardIterator
that accesses the individual matches of a regular expression within the underlying character sequence.
On construction, and on every increment, it calls std::regex_search and remembers the result (that is, saves a copy of the value std::match_results<BidirIt>). The first object may be read when the iterator is constructed or when the first dereferencing is done. Otherwise, dereferencing only returns a copy of the most recently obtained regex match.
The default-constructed std::regex_iterator
is the end-of-sequence iterator. When a valid std::regex_iterator
is incremented after reaching the last match (std::regex_search returns false), it becomes equal to the end-of-sequence iterator. Dereferencing or incrementing it further invokes undefined behavior.
A typical implementation of std::regex_iterator
holds the begin and the end iterators for the underlying sequence (two instances of BidirIt), a pointer to the regular expression (const regex_type*), the match flags (std::regex_constants::match_flag_type), and the current match (std::match_results<BidirIt>).
Type requirements
-BidirIt must meet the requirements of BidirectionalIterator .
|
Specializations
Several specializations for common character sequence types are defined:
Defined in header
<regex> | |
Type | Definition |
cregex_iterator
|
regex_iterator<const char*> |
wcregex_iterator
|
regex_iterator<const wchar_t*> |
sregex_iterator
|
regex_iterator<std::string::const_iterator> |
wsregex_iterator
|
regex_iterator<std::wstring::const_iterator> |
Member types
Member type | Definition |
value_type
|
std::match_results<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
constructs a new regex_iterator (public member function) | |
(destructor) (implicitly declared) |
destructs a regex_iterator , including the cached value (public member function) |
assigns contents (public member function) | |
compares two regex_iterator s (public member function) | |
accesses the current match (public member function) | |
advances the iterator to the next match (public member function) |
Notes
It is the programmer's responsibility to ensure that the std::basic_regex object passed to the iterator's constructor outlives the iterator. Because the iterator stores a pointer to the regex, incrementing the iterator after the regex was destroyed accesses a dangling pointer.
If the part of the regular expression that matched is just an assertion (^
, $
, \b
, \B
), the match stored in the iterator is a zero-length match, that is, match[0].first == match[0].second.
Example
#include <regex> #include <iterator> #include <iostream> #include <string> int main() { const std::string s = "Quick brown fox."; std::regex words_regex("[^\\s]+"); auto words_begin = std::sregex_iterator(s.begin(), s.end(), words_regex); auto words_end = std::sregex_iterator(); std::cout << "Found " << std::distance(words_begin, words_end) << " words:\n"; for (std::sregex_iterator i = words_begin; i != words_end; ++i) { std::smatch match = *i; std::string match_str = match.str(); std::cout << match_str << '\n'; } }
Output:
Found 3 words: Quick brown fox.
See also
(C++11) |
identifies one regular expression match, including all sub-expression matches (class template) |
(C++11) |
check if a regular expression occurs anywhere within a string (function template) |