std::match_results<BidirIt,Alloc>::operator[]

Since C++11

If n > 0 and n < size(), returns a reference to the std::sub_match representing the part of the target sequence that was matched by the nth captured marked subexpression).

# Declarations

const_reference operator[]( size_type n ) const;

(since C++11)

# Parameters

n: integral number specifying which match to return

# Return value

Reference to the std::sub_match representing the specified matched subrange within the target sequence.

# Example

#include <iostream>
#include <regex>
#include <string>
 
int main()
{
    std::string target("baaaby");
    std::smatch sm;
 
    std::regex re1("a(a)*b");
    std::regex_search(target, sm, re1);
    std::cout << "entire match: " << sm[0] << '\n'
              << "submatch #1: " << sm[1] << '\n';
 
    std::regex re2("a(a*)b");
    std::regex_search(target, sm, re2);
    std::cout << "entire match: " << sm[0] << '\n'
              << "submatch #1: " << sm[1] << '\n';
}