A freind fnction and a friend class

freindFunc.cpp

// A freind function

class A;
 
class B
{
private:
    int i_Num;
public:
    B(int iNum) { i_Num = iNum; }
 
    friend void PrintNumbers(A &a, B &b); // non-member function, cannot use this
};
 
class A
{
private:
    int i_Num;
public:
    A(int iNum) { i_Num = iNum; }
 
    friend void PrintNumbers(A &a, B &b);
};
 
void PrintNumbers(A &a, B &b)
{
    std::cout << "A number is " << a.i_Num <<
        " and the B number is " << b.i_Num << std::endl;
}

friendClass.cpp

// A freind class

class B
{
private:
    int i_Num;
public:
    B(int iNum) { i_Num = iNum; }
 
    friend class A;
};
 
class A {
private:
    int i_Num;
    
public:
    
    void PrintNumbers(B &b) {
        
        std::cout << "A number is " << i_Num <<
            " and the B number is " << b.i_Num << std::endl; // accessing the private member of B
        
    }   
}

Logger.cpp

#include <iostream>
#include <ctime>
#include <sstream>
#include <fstream>

using namespace std;

// timestamp returns the current time as a string
std::string timestamp();

class LogStatement;
ostream& operator<<(ostream& ost, const LogStatement& ls);

class LogStatement {
public:

    LogStatement(std::string s) : data(s), time_string(timestamp()) {
    };

    //This method handles all the outputs.   
    friend ostream& operator<<(ostream&, const LogStatement&);
private:
    std::string data;
    std::string time_string;

};

ostream& operator<<(ostream& ost, const LogStatement& ls) {
    ost << "~|" << ls.time_string << '|' << ls.data << "|~";
    return ost;
}

std::string timestamp() {
    //Notice the use of a stringstream, yet another useful stream medium!
    ostringstream stream;
    time_t rawtime;
    tm * timeinfo;

    time(&rawtime);
    timeinfo = localtime(&rawtime);

    stream << (timeinfo->tm_year) + 1900 << " " << timeinfo->tm_mon
            << " " << timeinfo->tm_mday << " " << timeinfo->tm_hour
            << " " << timeinfo->tm_min << " " << timeinfo->tm_sec;
    // The str() function of output stringstreams return a std::string.
    return stream.str();
}

/*
 * 
 */
int main(int argc, char** argv) {

    char* testArr[3] = {"log 1", "log 2", "log 3"};
    ostringstream log_data;
    // This takes all the char arrays in the argv
    // (except the filename) and produces a stream.
    for (int i = 0; i < 3; i++) {
        log_data << testArr[i] << ' ';
    }
    
    int iAnyNum=100;
    log_data << iAnyNum;

    LogStatement log_entry(log_data.str());

    clog << log_entry << endl;

    ofstream logfile("logfile", ios::app);

    // check for errors opening the file
    if (!logfile) {
        return -1;
    }

    logfile << log_entry << endl;
    logfile.close();

    return 0;
}