< cpp‎ | regex
Regular expressions library
Regex Grammar
Defined in header <regex>

    class BidirIt,
    class Alloc = std::allocator<std::sub_match<BidirIt>>

> class match_results;
(1) (since C++11)
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 std::sub_match (index 0) contained in a std::match_result always represents the full match within a target sequence made by a regex, and subsequent std::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.


[edit] Type requirements

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

[edit] Specializations

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>

[edit] 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>

[edit] Member functions

constructs the object
(public member function) [edit]
destructs the object
(public member function) [edit]
assigns the contents
(public member function) [edit]
returns the associated allocator
(public member function) [edit]
checks if the results are available
(public member function)
checks whether the match was successful
(public member function) [edit]
returns the number of matches in a fully-established result state
(public member function) [edit]
returns the maximum possible number of sub-matches
(public member function) [edit]
Element access
returns the length of the particular sub-match
(public member function) [edit]
returns the position of the first character of the particular sub-match
(public member function) [edit]
returns the sequence of characters for the particular sub-match
(public member function) [edit]
returns specified sub-match
(public member function) [edit]
returns sub-sequence between the beginning of the target sequence and the beginning of the full match
(public member function) [edit]
returns sub-sequence between the end of the full match and the end of the target sequence
(public member function) [edit]
returns iterator to the beginning of the list of sub-matches
(public member function) [edit]
returns iterator to the end of the list of sub-matches
(public member function) [edit]
formats match results for output
(public member function) [edit]
swaps the contents
(public member function) [edit]

[edit] Non-member functions

(removed in C++20)
lexicographically compares the values in the two match result
(function template) [edit]
specializes the std::swap algorithm
(function template) [edit]