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/C++

std::match_results::size

size_type size() const;

(since C++11)

Returns the number of submatches, i.e. std::distance(begin(), end()).

Returns 0 if *this does not represent the result of a successful match.

Parameters

(none).

Return value

The number of submatches.

Exceptions

noexcept specification:

noexcept

Complexity

Constant.

Example

#include <iostream>
#include <regex>
#include <string>
 
int main()
{
    std::regex re("a(a)*b");
    std::string target("aaab");
    std::smatch sm;
 
    std::cout << sm.size() << '\n';
 
    std::regex_match(target, sm, re);
    std::cout << sm.size() << '\n';
}

Output:

0
2