< cpp‎ | regex
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 [beginend) 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.


[edit] Type requirements

BidirIt must meet the requirements of LegacyBidirectionalIterator.

[edit] 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>

[edit] 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>

[edit] 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)

[edit] Member functions

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

[edit] 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) [edit]
outputs the matched character subsequence
(function template) [edit]

[edit] See also

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