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match_results begin() and end() function in C++ STL
In this article we will be discussing the working, syntax and examples of match_results::begin() and match_results::end() functions in C++ STL.
What is a match_results in C++ STL?
std::match_results is a specialized container-like class which is used to hold the collection of character sequences which are matched. In this container class a regex match operation finds the matches of the target sequence.
What is match_results::begin()?
match_results::begin() function is an inbuilt function in C++ STL, which is defined in <regex> header file. This function returns an iterator which is pointing to the first element in the match_results object. The match_results::begin() and match_results::end() are together used to give the range of the match_results container.
Syntax
match_name.begin();
Parameters
This function accepts no parameter.
Return value
This function returns an iterator which is pointing to the first element of the match_results container.
Example
Input: std::string str("TutorialsPoint");
std::smatch Mat;
std::regex re("(Tutorials)(.*)");
std::regex_match ( str, Mat, re );
Mat.begin();
Output: T
Example
#include <iostream>
#include <string>
#include <regex>
int main () {
std::string str("Tutorials");
std::smatch Mat;
std::regex re("(Tuto)(.*)");
std::regex_match ( str, Mat, re );
std::cout<<"Match Found: " << std::endl;
for (std::smatch::iterator i = Mat.begin(); i!= Mat.end(); ++i) {
std::cout << *i << std::endl;
}
return 0;
}
Output
If we run the above code it will generate the following output −
Match Found Tutorials Tuto rials
What is match_results::end()?
match_results::end() function is an inbuilt function in C++ STL, which is defined in <regex> header file. This function returns an iterator which is pointing to the position next to the last element in the match_results object. The match_results::begin() and match_results::end() are togetherly used to give the range of the match_results container.
Syntax
smatch_name.begin();
Parameters
This function accepts no parameter.
Return value
This function returns an iterator which is pointing to the element past the end of the match_results container.
Input: std::string str("TutorialsPoint");
std::smatch Mat;
std::regex re("(Tutorials)(.*)");
std::regex_match ( str, Mat, re );
Mat.end();
Output: m //Random value which is past to the end of the container.
Example
#include <iostream>
#include <string>
#include <regex>
int main () {
std::string str("Tutorials");
std::smatch Mat;
std::regex re("(Tuto)(.*)");
std::regex_match ( str, Mat, re );
std::cout<<"Match Found: " << std::endl;
for (std::smatch::iterator i = Mat.begin(); i!= Mat.end(); ++i) {
std::cout << *i << std::endl;
}
return 0;
}
Output
If we run the above code it will generate the following output −
Match Found Tutorials Tuto rials
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