std::sub_match
| Defined in header <regex>
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||
template< class BidirIt > class sub_match; |
(since C++11) | |
The class template std::sub_match is used by the regular expression engine to denote sequences of characters matched by marked sub-expressions.
A match is a [begin, end) pair within the target range matched by the regular expression, but with additional observer functions to enhance code clarity.
Only the default constructor is publicly accessible. Instances of std::sub_match are normally constructed and populated as a part of a std::match_results container during the processing of one of the regex algorithms.
The member functions return defined default values unless the matched member is true.
std::sub_match inherits from std::pair<BidirIt, BidirIt>, although it cannot be treated as a std::pair object because member functions such as assignment will not work as expected.
Type requirements
-BidirIt must meet the requirements of LegacyBidirectionalIterator.
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Specializations
Several specializations for common character sequence types are provided:
Defined in header
<regex> | |
| Type | Definition |
std::csub_match
|
std::sub_match<const char*>
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std::wcsub_match
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std::sub_match<const wchar_t*>
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std::ssub_match
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std::sub_match<std::string::const_iterator>
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std::wssub_match
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std::sub_match<std::wstring::const_iterator>
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Nested types
| Type | Definition |
iterator
|
BidirIt
|
value_type
|
std::iterator_traits<BidirIt>::value_type
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difference_type
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std::iterator_traits<BidirIt>::difference_type
|
string_type
|
std::basic_string<value_type>
|
Data members
| Member | Description |
matched |
whether this match was successful (public member object) |
Inherited from std::pair
BidirIt first |
start of the match sequence (public member object) |
BidirIt second |
one-past-the-end of the match sequence (public member object) |
Member functions
| constructs the match object (public member function) | |
Observers | |
| returns the length of the match (if any) (public member function) | |
| converts to the underlying string type (public member function) | |
| compares matched subsequence (if any) (public member function) | |
Modifiers | |
| swaps the contents (public member function) | |
Non-member functions
(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(removed in C++20)(C++20) |
compares a sub_match with another sub_match, a string, or a character (function template) |
| outputs the matched character subsequence (function template) |
Example
#include <cassert>
#include <iostream>
#include <regex>
#include <string>
int main()
{
std::string sentence{"Friday the thirteenth."};
const std::regex re{"([A-z]+) ([a-z]+) ([a-z]+)"};
std::smatch words;
std::regex_search(sentence, words, re);
std::cout << std::boolalpha;
for (const auto& m : words)
{
assert(m.matched);
std::cout << "m: [" << m << "], m.length(): " << m.length() << ", "
"*m.first: '" << *m.first << "', "
"*m.second: '" << *m.second << "'\n";
}
}
Output:
m: [Friday the thirteenth], m.length(): 21, *m.first: 'F', *m.second: '.'
m: [Friday], m.length(): 6, *m.first: 'F', *m.second: ' '
m: [the], m.length(): 3, *m.first: 't', *m.second: ' '
m: [thirteenth], m.length(): 10, *m.first: 't', *m.second: '.'
See also
(C++11) |
iterates through the specified sub-expressions within all regex matches in a given string or through unmatched substrings (class template) |