31 Regular expressions library [re]

31.11 Regular expression algorithms [re.alg]

31.11.1 Exceptions [re.except]

The algorithms described in this subclause may throw an exception of type regex_­error.
If such an exception e is thrown, e.code() shall return either regex_­constants​::​error_­complexity or regex_­constants​::​error_­stack.

31.11.2 regex_­match [re.alg.match]

template<class BidirectionalIterator, class Allocator, class charT, class traits> bool regex_match(BidirectionalIterator first, BidirectionalIterator last, match_results<BidirectionalIterator, Allocator>& m, const basic_regex<charT, traits>& e, regex_constants::match_flag_type flags = regex_constants::match_default);
Requires: The type BidirectionalIterator shall satisfy the requirements of a Bidirectional Iterator.
Effects: Determines whether there is a match between the regular expression e, and all of the character sequence [first, last).
The parameter flags is used to control how the expression is matched against the character sequence.
When determining if there is a match, only potential matches that match the entire character sequence are considered.
Returns true if such a match exists, false otherwise.
[Example
:
std::regex re("Get|GetValue");
std::cmatch m;
regex_search("GetValue", m, re);	// returns true, and m[0] contains "Get"
regex_match ("GetValue", m, re);	// returns true, and m[0] contains "GetValue"
regex_search("GetValues", m, re);	// returns true, and m[0] contains "Get"
regex_match ("GetValues", m, re);	// returns false
end example
]
Postconditions: m.ready() == true in all cases.
If the function returns false, then the effect on parameter m is unspecified except that m.size() returns 0 and m.empty() returns true.
Otherwise the effects on parameter m are given in Table 127.
Table 127 — Effects of regex_­match algorithm
Element
Value
m.size()
1 + e.mark_­count()
m.empty()
false
m.prefix().first
first
m.prefix().second
first
m.prefix().matched
false
m.suffix().first
last
m.suffix().second
last
m.suffix().matched
false
m[0].first
first
m[0].second
last
m[0].matched
true
m[n].first
For all integers 0 < n < m.size(), the start of the sequence that matched sub-expression n.
Alternatively, if sub-expression n did not participate in the match, then last.
m[n].second
For all integers 0 < n < m.size(), the end of the sequence that matched sub-expression n.
Alternatively, if sub-expression n did not participate in the match, then last.
m[n].matched
For all integers 0 < n < m.size(), true if sub-expression n participated in the match, false otherwise.
template<class BidirectionalIterator, class charT, class traits> bool regex_match(BidirectionalIterator first, BidirectionalIterator last, const basic_regex<charT, traits>& e, regex_constants::match_flag_type flags = regex_constants::match_default);
Effects: Behaves “as if” by constructing an instance of match_­results<BidirectionalIterator> what, and then returning the result of regex_­match(first, last, what, e, flags).
template<class charT, class Allocator, class traits> bool regex_match(const charT* str, match_results<const charT*, Allocator>& m, const basic_regex<charT, traits>& e, regex_constants::match_flag_type flags = regex_constants::match_default);
Returns: regex_­match(str, str + char_­traits<charT>​::​length(str), m, e, flags).
template<class ST, class SA, class Allocator, class charT, class traits> bool regex_match(const basic_string<charT, ST, SA>& s, match_results<typename basic_string<charT, ST, SA>::const_iterator, Allocator>& m, const basic_regex<charT, traits>& e, regex_constants::match_flag_type flags = regex_constants::match_default);
Returns: regex_­match(s.begin(), s.end(), m, e, flags).
template<class charT, class traits> bool regex_match(const charT* str, const basic_regex<charT, traits>& e, regex_constants::match_flag_type flags = regex_constants::match_default);
Returns: regex_­match(str, str + char_­traits<charT>​::​length(str), e, flags)
template<class ST, class SA, class charT, class traits> bool regex_match(const basic_string<charT, ST, SA>& s, const basic_regex<charT, traits>& e, regex_constants::match_flag_type flags = regex_constants::match_default);
Returns: regex_­match(s.begin(), s.end(), e, flags).

31.11.4 regex_­replace [re.alg.replace]

template<class OutputIterator, class BidirectionalIterator, class traits, class charT, class ST, class SA> OutputIterator regex_replace(OutputIterator out, BidirectionalIterator first, BidirectionalIterator last, const basic_regex<charT, traits>& e, const basic_string<charT, ST, SA>& fmt, regex_constants::match_flag_type flags = regex_constants::match_default); template<class OutputIterator, class BidirectionalIterator, class traits, class charT> OutputIterator regex_replace(OutputIterator out, BidirectionalIterator first, BidirectionalIterator last, const basic_regex<charT, traits>& e, const charT* fmt, regex_constants::match_flag_type flags = regex_constants::match_default);
Effects: Constructs a regex_­iterator object i as if by
regex_iterator<BidirectionalIterator, charT, traits> i(first, last, e, flags)
and uses i to enumerate through all of the matches m of type match_­results<BidirectionalIterator> that occur within the sequence [first, last).
If no such matches are found and !(flags & regex_­constants​::​format_­no_­copy), then calls
out = copy(first, last, out)
If any matches are found then, for each such match:
  • If !(flags & regex_­constants​::​format_­no_­copy), calls
    out = copy(m.prefix().first, m.prefix().second, out)
  • Then calls
    out = m.format(out, fmt, flags)
    for the first form of the function and
    out = m.format(out, fmt, fmt + char_traits<charT>::length(fmt), flags)
    for the second.
Finally, if such a match is found and !(flags & regex_­constants​::​format_­no_­copy), calls
out = copy(last_m.suffix().first, last_m.suffix().second, out)
where last_­m is a copy of the last match found.
If flags & regex_­constants​::​format_­first_­only is nonzero, then only the first match found is replaced.
Returns: out.
template<class traits, class charT, class ST, class SA, class FST, class FSA> basic_string<charT, ST, SA> regex_replace(const basic_string<charT, ST, SA>& s, const basic_regex<charT, traits>& e, const basic_string<charT, FST, FSA>& fmt, regex_constants::match_flag_type flags = regex_constants::match_default); template<class traits, class charT, class ST, class SA> basic_string<charT, ST, SA> regex_replace(const basic_string<charT, ST, SA>& s, const basic_regex<charT, traits>& e, const charT* fmt, regex_constants::match_flag_type flags = regex_constants::match_default);
Effects: Constructs an empty string result of type basic_­string<charT, ST, SA> and calls:
regex_replace(back_inserter(result), s.begin(), s.end(), e, fmt, flags);
Returns: result.
template<class traits, class charT, class ST, class SA> basic_string<charT> regex_replace(const charT* s, const basic_regex<charT, traits>& e, const basic_string<charT, ST, SA>& fmt, regex_constants::match_flag_type flags = regex_constants::match_default); template<class traits, class charT> basic_string<charT> regex_replace(const charT* s, const basic_regex<charT, traits>& e, const charT* fmt, regex_constants::match_flag_type flags = regex_constants::match_default);
Effects: Constructs an empty string result of type basic_­string<charT> and calls:
regex_replace(back_inserter(result), s, s + char_traits<charT>::length(s), e, fmt, flags);
Returns: result.