28 Text processing library [text]
28.6 Regular expressions library [re]
28.6.10 Regular expression algorithms [re.alg]
28.6.10.1 Exceptions [re.except]
28.6.10.2 regex_match [re.alg.match]
28.6.10.3 regex_search [re.alg.search]
28.6.10.4 regex_replace [re.alg.replace]
28.6.10.1 Exceptions [re.except]
The algorithms described in subclause [re.alg] 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.
28.6.10.2 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);
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 1: std::regex re("Get|GetValue"); std::cmatch m; regex_search("GetValue", m, re); regex_match ("GetValue", m, re); regex_search("GetValues", m, re); regex_match ("GetValues", m, re); — 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 123.
Table 123 — Effects of regex_match algorithm [tab:re.alg.match]
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 | |
m[n].second | |
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).
28.6.10.3 regex_search [re.alg.search]
template<class BidirectionalIterator, class Allocator, class charT, class traits>
bool regex_search(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);
Effects: Determines whether there is some sub-sequence within [first, last) that matches the regular expression e.
The parameter flags is used to control how the expression is matched against the character sequence.
Returns true if such a sequence exists, false otherwise.
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 124.
Table 124 — Effects of regex_search algorithm [tab:re.alg.search]
Element | Value |
m.size() | 1 + e.mark_count() |
m.empty() | false |
m.prefix().first | first |
m.prefix().second | m[0].first |
m.prefix().matched | m.prefix().first != m.prefix().second |
m.suffix().first | m[0].second |
m.suffix().second | last |
m.suffix().matched | m.suffix().first != m.suffix().second |
m[0].first | The start of the sequence of characters that matched the regular expression |
m[0].second | The end of the sequence of characters that matched the regular expression |
m[0].matched | true |
m[n].first | |
m[n].second | |
m[n].matched | For all integers 0 < n < m.size(), true if sub-expression n participated in the match, false otherwise. |
template<class charT, class Allocator, class traits>
bool regex_search(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_search(str, str + char_traits<charT>::length(str), m, e, flags).
template<class ST, class SA, class Allocator, class charT, class traits>
bool regex_search(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_search(s.begin(), s.end(), m, e, flags).
template<class BidirectionalIterator, class charT, class traits>
bool regex_search(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 object what of type match_results<BidirectionalIterator> and returning regex_search(first, last, what, e, flags).
template<class charT, class traits>
bool regex_search(const charT* str,
const basic_regex<charT, traits>& e,
regex_constants::match_flag_type flags = regex_constants::match_default);
Returns: regex_search(str, str + char_traits<charT>::length(str), e, flags).
template<class ST, class SA, class charT, class traits>
bool regex_search(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_search(s.begin(), s.end(), e, flags).
28.6.10.4 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.
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);
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);