202                                             7. Ad hoc 

class clock {

clock operator -(clock c);

clock clock::operator-(clock c)

{

return (tot_secs - c.tot_secs);

}

,     .    -
 .        
 -    .

     ,  
   unsigned long,      clock.  
   ,     
-,   ,     
.

class clock {

friend clock operator*(unsigned long m, clock c);

};

clock operator*(unsigned long m, clock c)
{

return (m * c.tot_secs) ;

}

           -
.         :

clock operator*(clock , unsigned long m)
{

return (m * c.tot_secs);

}

  ,      :

clock operator*(clock , unsigned long m)

{

return (m * c);

}

    ,       
   .

7.7.     

        -
    .  ,  
 .    my_string  vect, 