Class template match_results denotes a collection of character sequences representing the result of a regular expression match. Storage for the collection is allocated and freed as necessary by the member functions of class template match_results.
The class template match_results satisfies the requirements of an allocator-aware container and of a sequence container ([container.requirements.general], [sequence.reqmts]) except that only operations defined for const-qualified sequence containers are supported and that the semantics of comparison functions are different from those required for a container.
A default-constructed match_results object has no fully established result state. A match result is ready when, as a consequence of a completed regular expression match modifying such an object, its result state becomes fully established. The effects of calling most member functions from a match_results object that is not ready are undefined.
The sub_match object stored at index 0 represents sub-expression 0, i.e., the whole match. In this case the sub_match member matched is always true. The sub_match object stored at index n denotes what matched the marked sub-expression n within the matched expression. If the sub-expression n participated in a regular expression match then the sub_match member matched evaluates to true, and members first and second denote the range of characters [first, second) which formed that match. Otherwise matched is false, and members first and second point to the end of the sequence that was searched. [ Note: The sub_match objects representing different sub-expressions that did not participate in a regular expression match need not be distinct. — end note ]
namespace std {
template <class BidirectionalIterator,
class Allocator = allocator<sub_match<BidirectionalIterator>>>
class match_results {
public:
using value_type = sub_match<BidirectionalIterator>;
using const_reference = const value_type&;
using reference = value_type&;
using const_iterator = implementation-defined;
using iterator = const_iterator;
using difference_type =
typename iterator_traits<BidirectionalIterator>::difference_type;
using size_type = typename allocator_traits<Allocator>::size_type;
using allocator_type = Allocator;
using char_type =
typename iterator_traits<BidirectionalIterator>::value_type;
using string_type = basic_string<char_type>;
explicit match_results(const Allocator& a = Allocator());
match_results(const match_results& m);
match_results(match_results&& m) noexcept;
match_results& operator=(const match_results& m);
match_results& operator=(match_results&& m);
~match_results();
bool ready() const;
size_type size() const;
size_type max_size() const;
bool empty() const;
difference_type length(size_type sub = 0) const;
difference_type position(size_type sub = 0) const;
string_type str(size_type sub = 0) const;
const_reference operator[](size_type n) const;
const_reference prefix() const;
const_reference suffix() const;
const_iterator begin() const;
const_iterator end() const;
const_iterator cbegin() const;
const_iterator cend() const;
template <class OutputIter>
OutputIter
format(OutputIter out,
const char_type* fmt_first, const char_type* fmt_last,
regex_constants::match_flag_type flags = regex_constants::format_default) const;
template <class OutputIter, class ST, class SA>
OutputIter
format(OutputIter out,
const basic_string<char_type, ST, SA>& fmt,
regex_constants::match_flag_type flags = regex_constants::format_default) const;
template <class ST, class SA>
basic_string<char_type, ST, SA>
format(const basic_string<char_type, ST, SA>& fmt,
regex_constants::match_flag_type flags = regex_constants::format_default) const;
string_type
format(const char_type* fmt,
regex_constants::match_flag_type flags = regex_constants::format_default) const;
allocator_type get_allocator() const;
void swap(match_results& that);
};
}31.10.1 match_results constructors [re.results.const]
In all match_results constructors, a copy of the Allocator argument shall be used for any memory allocation performed by the constructor or member functions during the lifetime of the object.
match_results(const Allocator& a = Allocator());
Effects: Constructs an object of class match_results.
Postconditions: ready() returns false. size() returns 0.
match_results(const match_results& m);
Effects: Constructs an object of class match_results, as a copy of m.
match_results(match_results&& m) noexcept;
Effects: Move constructs an object of class match_results from m satisfying the same postconditions as Table 134. Additionally, the stored Allocator value is move constructed from m.get_allocator().
match_results& operator=(const match_results& m);
Effects: Assigns m to *this. The postconditions of this function are indicated in Table 134.
match_results& operator=(match_results&& m);
Effects: Move-assigns m to *this. The postconditions of this function are indicated in Table 134.
Table
134—
match_resultsassignment operator effects
bool ready() const;
Returns: true if *this has a fully established result state, otherwise false.
31.10.3 match_results size [re.results.size]size_type size() const;
Returns: One plus the number of marked sub-expressions in the regular expression that was matched if *this represents the result of a successful match. Otherwise returns 0. [ Note: The state of a match_results object can be modified only by passing that object to regex_match or regex_search. Sections [re.alg.match] and [re.alg.search] specify the effects of those algorithms on their match_results arguments. — end note ]
size_type max_size() const;
Returns: The maximum number of sub_match elements that can be stored in *this.
bool empty() const;
difference_type length(size_type sub = 0) const;
Requires: ready() == true.
Returns: (*this)[sub].length().
difference_type position(size_type sub = 0) const;
Requires: ready() == true.
Returns: The distance from the start of the target sequence to (*this)[sub].first.
string_type str(size_type sub = 0) const;
Requires: ready() == true.
Returns: string_type((*this)[sub]).
const_reference operator[](size_type n) const;
Requires: ready() == true.
Returns: A reference to the sub_match object representing the character sequence that matched marked sub-expression n. If n == 0 then returns a reference to a sub_match object representing the character sequence that matched the whole regular expression. If n >= size() then returns a sub_match object representing an unmatched sub-expression.
const_reference prefix() const;
Requires: ready() == true.
Returns: A reference to the sub_match object representing the character sequence from the start of the string being matched/searched to the start of the match found.
const_reference suffix() const;
Requires: ready() == true.
Returns: A reference to the sub_match object representing the character sequence from the end of the match found to the end of the string being matched/searched.
const_iterator begin() const; const_iterator cbegin() const;
Returns: A starting iterator that enumerates over all the sub-expressions stored in *this.
const_iterator end() const; const_iterator cend() const;
Returns: A terminating iterator that enumerates over all the sub-expressions stored in *this.
31.10.5 match_results formatting [re.results.form]template <class OutputIter> OutputIter format( OutputIter out, const char_type* fmt_first, const char_type* fmt_last, regex_constants::match_flag_type flags = regex_constants::format_default) const;
Requires: ready() == true and OutputIter shall satisfy the requirements for an Output Iterator.
Effects: Copies the character sequence [fmt_first, fmt_last) to OutputIter out. Replaces each format specifier or escape sequence in the copied range with either the character(s) it represents or the sequence of characters within *this to which it refers. The bitmasks specified in flags determine which format specifiers and escape sequences are recognized.
template <class OutputIter, class ST, class SA> OutputIter format( OutputIter out, const basic_string<char_type, ST, SA>& fmt, regex_constants::match_flag_type flags = regex_constants::format_default) const;
Effects: Equivalent to:
return format(out, fmt.data(), fmt.data() + fmt.size(), flags);
template <class ST, class SA> basic_string<char_type, ST, SA> format( const basic_string<char_type, ST, SA>& fmt, regex_constants::match_flag_type flags = regex_constants::format_default) const;
Requires: ready() == true.
Effects: Constructs an empty string result of type basic_string<char_type, ST, SA> and calls:
format(back_inserter(result), fmt, flags);
string_type format( const char_type* fmt, regex_constants::match_flag_type flags = regex_constants::format_default) const;
Requires: ready() == true.
Effects: Constructs an empty string result of type string_type and calls:
format(back_inserter(result), fmt, fmt + char_traits<char_type>::length(fmt), flags);31.10.6 match_results allocator [re.results.all]
allocator_type get_allocator() const;
Returns: A copy of the Allocator that was passed to the object's constructor or, if that allocator has been replaced, a copy of the most recent replacement.
31.10.7 match_results swap [re.results.swap]void swap(match_results& that);
Effects: Swaps the contents of the two sequences.
Postconditions: *this contains the sequence of matched sub-expressions that were in that, that contains the sequence of matched sub-expressions that were in *this.
Complexity: Constant time.
template <class BidirectionalIterator, class Allocator> void swap(match_results<BidirectionalIterator, Allocator>& m1, match_results<BidirectionalIterator, Allocator>& m2);
Effects: As if by m1.swap(m2).
31.10.8 match_results non-member functions [re.results.nonmember]template <class BidirectionalIterator, class Allocator> bool operator==(const match_results<BidirectionalIterator, Allocator>& m1, const match_results<BidirectionalIterator, Allocator>& m2);
Returns: true if neither match result is ready, false if one match result is ready and the other is not. If both match results are ready, returns true only if:
m1.empty() && m2.empty(), or
!m1.empty() && !m2.empty(), and the following conditions are satisfied:
m1.prefix() == m2.prefix(),
m1.size() == m2.size() && equal(m1.begin(), m1.end(), m2.begin()), and
m1.suffix() == m2.suffix().
[ Note: The algorithm equal is defined in Clause [algorithms]. — end note ]
template <class BidirectionalIterator, class Allocator> bool operator!=(const match_results<BidirectionalIterator, Allocator>& m1, const match_results<BidirectionalIterator, Allocator>& m2);
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