std:: sub_match

Defined in header <regex>
template < class BidirIt > class sub_match ;		(since C++11)

The class template std::sub_match is used by the regular expression engine to denote sequences of characters matched by marked sub-expressions. A match is a [ begin , end ) pair within the target range matched by the regular expression, but with additional observer functions to enhance code clarity.

Only the default constructor is publicly accessible. Instances of std::sub_match are normally constructed and populated as a part of a std::match_results container during the processing of one of the regex algorithms.

The member functions return defined default values unless the matched member is true .

std::sub_match inherits from std:: pair < BidirIt, BidirIt > , although it cannot be treated as a std::pair object because member functions such as assignment will not work as expected.

Type requirements

- BidirIt must meet the requirements of LegacyBidirectionalIterator .

Specializations

Several specializations for common character sequence types are provided:

Defined in header <regex>
Type	Definition
std::csub_match	std :: sub_match < const char * >
std::wcsub_match	std :: sub_match < const wchar_t * >
std::ssub_match	std :: sub_match < std :: string :: const_iterator >
std::wssub_match	std :: sub_match < std :: wstring :: const_iterator >

Nested types

Type	Definition
iterator	BidirIt
value_type	std:: iterator_traits < BidirIt > :: value_type
difference_type	std:: iterator_traits < BidirIt > :: difference_type
string_type	std:: basic_string < value_type >

Data members

Member	Description
bool matched	whether this match was successful

Member functions

This section is incomplete Reason: Apply LWG 3204, add the swap() member function

(constructor)	constructs the match object (public member function)
Observers
length	returns the length of the match (if any) (public member function)
str operator string_type	converts to the underlying string type (public member function)
compare	compares matched subsequence (if any) (public member function)

Non-member functions

operator== operator!= operator< operator<= operator> operator>= operator<=> (removed in C++20) (removed in C++20) (removed in C++20) (removed in C++20) (removed in C++20) (C++20)	compares a sub_match with another sub_match , a string, or a character (function template)
operator<<	outputs the matched character subsequence (function template)

See also

regex_token_iterator (C++11)

iterates through the specified sub-expressions within all regex matches in a given string or through unmatched substrings (class template)