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std::match_results(3) C++ Standard Libary std::match_results(3)


std::match_results - std::match_results


Defined in header <regex>

class BidirIt, (1) (since C++11)
class Alloc = std::allocator<std::sub_match<BidirIt>>

> class match_results;
namespace pmr {

template <class BidirIt>
using match_results = std::match_results<BidirIt, (2) (since C++17)


The class template std::match_results holds a collection of character sequences that
represent the result of a regular expression match.

This is a specialized allocator-aware container. It can only be default created,
obtained from std::regex_iterator, or modified by std::regex_search or
std::regex_match. Because std::match_results holds std::sub_matches, each of which
is a pair of iterators into the original character sequence that was matched, it's
undefined behavior to examine std::match_results if the original character sequence
was destroyed or iterators to it were invalidated for other reasons.

The first sub_match (index 0) contained in a match_result always represents the full
match within a target sequence made by a regex, and subsequent sub_matches represent
sub-expression matches corresponding in sequence to the left parenthesis delimiting
the sub-expression in the regex.

std::match_results meets the requirements of a AllocatorAwareContainer and of a
SequenceContainer, except that only copy assignment, move assignment, and operations
defined for a constant containers are supported, and that the semantics of
comparison functions are different from those required for a container.

Type requirements

BidirIt must meet the requirements of LegacyBidirectionalIterator.
Alloc must meet the requirements of Allocator.


Several specializations for common character sequence types are provided:

Defined in header <regex>
Type Definition
std::cmatch std::match_results<const char*>
std::wcmatch std::match_results<const wchar_t*>
std::smatch std::match_results<std::string::const_iterator>
std::wsmatch std::match_results<std::wstring::const_iterator>
std::pmr::cmatch (C++17) std::pmr::match_results<const char*>
std::pmr::wcmatch (C++17) std::pmr::match_results<const wchar_t*>
std::pmr::smatch (C++17) std::pmr::match_results<std::string::const_iterator>
std::pmr::wsmatch (C++17) std::pmr::match_results<std::wstring::const_iterator>

Member types

Member type Definition
allocator_type Allocator
value_type std::sub_match<BidirIt>
const_reference const value_type&
reference value_type&
const_iterator implementation defined (depends on the underlying container)
iterator const_iterator
difference_type std::iterator_traits<BidirIt>::difference_type
size_type std::allocator_traits<Alloc>::size_type
char_type std::iterator_traits<BidirIt>::value_type
string_type std::basic_string<char_type>

Member functions

constructor constructs the object
(public member function)
destructor destructs the object
(public member function)
operator= assigns the contents
(public member function)
get_allocator returns the associated allocator
(public member function)


ready checks if the results are available
(public member function)


empty checks whether the match was successful
(public member function)
size returns the number of matches in a fully-established result state
(public member function)
max_size returns the maximum possible number of sub-matches
(public member function)

Element access

length returns the length of the particular sub-match
(public member function)
returns the position of the first character of the particular
position sub-match
(public member function)
str returns the sequence of characters for the particular sub-match
(public member function)
operator[] returns specified sub-match
(public member function)
returns sub-sequence between the beginning of the target sequence and
prefix the beginning of the full match.
(public member function)
returns sub-sequence between the end of the full match and the end of
suffix the target sequence
(public member function)


begin returns iterator to the beginning of the list of sub-matches
cbegin (public member function)
end returns iterator to the end of the list of sub-matches
cend (public member function)


format formats match results for output
(public member function)


swap swaps the contents
(public member function)

Non-member functions

operator== lexicographically compares the values in the two match
operator!= result
(removed in C++20) (function template)
std::swap(std::match_results) specializes the std::swap algorithm
(C++11) (function template)