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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>

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)

Inherited from std::pair

BidirIt first
Start of the match sequence.
(public member object)
BidirIt second
One-past-the-end of the match sequence.
(public member object)

Member functions

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

Non-member functions

(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)
outputs the matched character subsequence
(function template)

See also

(C++11)
iterates through the specified sub-expressions within all regex matches in a given string or through unmatched substrings
(class template)

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