match_results cbegin() add cend() in C++ STL

Last Updated : 21 Aug, 2018

match_results::cbegin() is an inbulit function in C++ STL which returns a constant iterator that points to the first match in the match_results object. This iterator cannot modify the contents of the vector.
Syntax:

smatch_name.cbegin()

Parameters: This function does not accept any parameters.

Return value: This function returns a constant iterator pointing to the first match in the match_results object. The matches contained in the match_results object are always constant.

Note: First element always contains the whole regex match while the others contain the particular Capturing Group.

Below program illustrate the above function.

// C++ program to illustrate the 
// match_result function 
#include <bits/stdc++.h>
using namespace std;
int main()
{
    string sp("geeksforgeeks");
    regex re("(geeks)(.*)");
  
    smatch match;
  
    // we can use member function on match
    // to extract the matched pattern.
    std::regex_match(sp, match, re);
  
    // The size() member function indicates the
    // number of capturing groups plus one for the overall match
    // match size = Number of capturing group + 1
    // (.*) which "forgeeks" ).
    cout << "Match size = " << match.size() << endl;
  
    cout << "matches:" << endl;
    for (smatch::iterator it = match.cbegin(); it != match.cend(); ++it)
        cout << *it << endl;
    return 0;
}

Output:

Match size=3
matches:
geeksforgeeks
geeks
forgeeks

smatch::cend() is an inbulit function in C++ STL which returns a constant iterator that points to the past-the-end match in the match_results object. This iterator cannot modify the contents of the vector.

Syntax:

smatch_name.cend()

Parameters: This function does not accept any parameters.

Return value: This function returns a constant iterator pointing to the past-the-end match in the match_results object. The matches contained in the match_results object are always constant.

Note: First element always contains the whole regex match while the others contain the particular Capturing Group.

Below program illustrate the above function

// C++ program to illustrate the 
// match_results cend() function 
#include <bits/stdc++.h>
using namespace std;
int main()
{
    string sp("matchresult");
    regex re("(match)(.*)");
  
    smatch match;
  
    // we can use member function on match
    // to extract the matched pattern.
    std::regex_match(sp, match, re);
  
    // The size() member function indicates the
    // number of capturing groups plus one for the overall match
    // match size = Number of capturing group + 1
    // (.*) which "results" ).
    cout << "Match size = " << match.size() << endl;
  
    cout << "matches:" << endl;
    for (smatch::iterator it = match.cbegin(); it != match.cend(); ++it)
        cout << *it << endl;
    return 0;
}

Output:

Match size=3
matches:
matchresults
match
results

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match_results cbegin() add cend() in C++ STL