std::sub_match

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

The class template 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 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.

sub_match inherits from std::pair<BidirIt, BidirIt>, although it cannot be treated as a std::pair object because member functions such as swap and 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
csub_match	sub_match<const char*>
wcsub_match	sub_match<const wchar_t*>
ssub_match	sub_match<std::string::const_iterator>
wssub_match	sub_match<std::wstring::const_iterator>

Member types

Member 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>

Member objects

bool matched

Indicates if this match was successful (public member object)

Member functions

(constructor)	constructs the match object (public member function)
Observers
length	returns the length of the match (if any) (public member function)
stroperator 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)