Есть готовый пример.Создание функций friend

[Oleg_SK]

#ifndef MYTIME3_H_
#define MYTIME3_H_
#include <iostream>

class Time
{
private:
       ...
public:
       ...
       ...
    //friends
    friend Time operator+(const Time & t1, const Time & t2);
    friend Time operator-(const Time & t1, const Time & t2);
    friend Time operator*(double m, const Time & t)
    { 
        return t * m;
    } 
    friend Time operator*(const Time & t, double mult);
    friend std::ostream & operator<<(std::ostream & os, const Time & t);

};
****************
#include "mytime3.h"

Time::Time()
{
    
}

Time::Time(int h, int m )
{
   
}

void Time::AddMin(int m)
{
  
}

void Time::AddHr(int h)
{

}

void Time::Reset(int h, int m)
{
   ...
}

Time operator+(const Time & t1, const Time & t2)
 {          
            int m = t1.minutes + t2.minutes;
             int op_m = m % 60; 
            int h = t1.hours + t2.hours + m / 60;
            Time sum(h, op_m);
            return sum;
 }
Time operator-(const Time & t1, const Time & t2)
 { 
             int st1 = (t1.hours * 60) + t1.minutes;
             int st2 = (t2.hours * 60) + t2.minutes;
             int h = (st1 - st2) / 60;
             int m = (st1 - st2) % 60;
             Time sum(h, m);
             return sum;
 }

Time operator*(const Time & t, double mult);
	{ 
		Time result;
		long totalminutes = t.hours * mult * 60 + t.minutes * mult;
		result.hours = totalminutes / 60;
		result.minutes = totalminutes % 60;
		return result;
	} 


std::ostream & operator<<(std::ostream & os, const Time & t)
{
    ...
}

**********
#include <iostream>
#include "mytime3.h"

using namespace std;

int main(int argc, char *argv[])
{
    using std::cout;
    using std::endl;
    Time aida(3, 35);
    Time tosca(2, 48);
    Time temp;

    cout << "Aida and Tosca:\n";
    cout << aida<<"; " << tosca << endl;
    temp = aida + tosca;
    cout << "Aida + Tosca: " << temp << endl;
    temp = aida * 1.17;
    cout << "Aida * 1.17: " << temp << endl;
    cout << "10 * Tosca: " << 10 * tosca << endl;
    temp = aida - tosca;
    cout<<"Aida - Tosca:"<< temp << endl;
    system("PAUSE");
    return EXIT_SUCCESS;
}