std:: match_results

Defined in header <regex>
template < 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, std:: pmr :: polymorphic_allocator < std:: sub_match < 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_match es, 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_match es 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 .

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 >

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)
State
ready	checks if the results are available (public member function)
Size
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)
position	returns the position of the first character of the particular 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)
prefix	returns sub-sequence between the beginning of the target sequence and the beginning of the full match (public member function)
suffix	returns sub-sequence between the end of the full match and the end of the target sequence (public member function)
Iterators
begin cbegin	returns iterator to the beginning of the list of sub-matches (public member function)
end cend	returns iterator to the end of the list of sub-matches (public member function)
Format
format	formats match results for output (public member function)
Modifiers
swap	swaps the contents (public member function)

Non-member functions

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