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 shall satisfy the requirements of an allocator-aware container and of a sequence container, as specified in [sequence.reqmts], except that only operations defined for const-qualified sequence containers are supported.
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: typedef sub_match<BidirectionalIterator> value_type; typedef const value_type& const_reference; typedef const_reference reference; typedef implementation-defined const_iterator; typedef const_iterator iterator; typedef typename iterator_traits<BidirectionalIterator>::difference_type difference_type; typedef typename allocator_traits<Allocator>::size_type size_type; typedef Allocator allocator_type; typedef typename iterator_traits<BidirectionalIterator>:: value_type char_type; typedef basic_string<char_type> string_type; // [re.results.const], construct/copy/destroy: 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(); // [re.results.state], state: bool ready() const; // [re.results.size], size: size_type size() const; size_type max_size() const; bool empty() const; // [re.results.acc], element access: 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; // [re.results.form], format: 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; // [re.results.all], allocator: allocator_type get_allocator() const; // [re.results.swap], swap: void swap(match_results& that); }; }
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.
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 [tab:re:results:assign]. Additionally, the stored Allocator value is move constructed from m.get_allocator().
Throws: Nothing if the allocator's move constructor throws nothing.
match_results& operator=(const match_results& m);
Effects: Assigns m to *this. The postconditions of this function are indicated in Table [tab:re:results:assign].
match_results& operator=(match_results&& m);
Effects: Move-assigns m to *this. The postconditions of this function are indicated in Table [tab:re:results:assign].
Element | Value |
ready() | m.ready() |
size() | m.size() |
str(n) | m.str(n) for all integers n < m.size() |
prefix() | m.prefix() |
suffix() | m.suffix() |
(*this)[n] | m[n] for all integers n < m.size() |
length(n) | m.length(n) for all integers n < m.size() |
position(n) | m.position(n) for all integers n < m.size() |
Returns: true if *this has a fully established result state, otherwise false.
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 ]
Returns: The maximum number of sub_match elements that can be stored in *this.
Returns: size() == 0.
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.
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 ([output.iterators]).
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.
Returns: out.
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).
Returns: result.
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).
Returns: result.
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.
void swap(match_results& that);
Effects: Swaps the contents of the two sequences.
Postcondition: *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: m1.swap(m2).
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);
Returns: !(m1 == m2).