Const Reference Params

Const references let a function read an existing object without copying or modifying it.

const_reference_params.cpp

#include <iostream>
#include <string>

int label_size(const std::string& label) {
    return static_cast<int>(label.size());
}

int main() {
    std::string label = ;

    int size = label_size(label);

    std::cout << "label=" << label << std::endl;
    std::cout << "size=" << size << std::endl;
    return 0;
}

#include <iostream>
#include <string>

int label_size(const std::string& label) {
    return static_cast<int>(label.size());
}

int main() {
    std::string label = ;

    int size = label_size(label);

    std::cout << "label=" << label << std::endl;
    std::cout << "size=" << size << std::endl;
    return 0;
}

#include <iostream>
#include <string>

int label_size(const std::string& label) {
    return static_cast<int>(label.size());
}

int main() {
    std::string label = ;

    int size = label_size(label);

    std::cout << "label=" << label << std::endl;
    std::cout << "size=" << size << std::endl;
    return 0;
}

const reference A const reference parameter can bind to an existing object while promising not to change it.

read-only parameter Read-only parameters are useful for strings and containers that should not be copied just to inspect them.