std::sub_match

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 )

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

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

Type requirements

Specializations

Several specializations for common character sequence types are provided:

Nested types

Data members

Member functions

Non-member functions

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";
    }
}

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