C++: Example of class with ctor, increment operator (prefix and suffix) and ostream overloading.

// simple Int class with ctor, increment operator and ostream overload 
class Int{
public:
    Int& operator++();
    const Int operator++( int n );
    
    Int(int i): _i(i) { };

    friend ostream& operator <<(ostream& os, const Int &i);
private:
    int _i;
};

// look difference between return values: Int& (in prefix)
Int& Int::operator++() {
    _i++;       // Handle case where no argument is passed.
    return *this;
}

// and const Int (in postfix)
const Int Int::operator++( int n ) {
    Int tmp(*this);

    if( n != 0 )
        for (int nr=0; nr<n; ++nr, ++(*this));
    else 
        ++(*this);

    return tmp;
}

// overloading << operator for Int class
ostream& operator <<(ostream& os, const Int &i) {
    os << i._i;
    return os;
}

void main() {

   Int gg(0);
   cout << gg.operator++(25) << endl ;    // Increment by 25 but shown 0
   cout << gg << endl;                    // in next reference is shown as 25

   // gg = 25
   cout << gg++ << endl;    // gg is 25. Only in the next reference will it be 26
   cout << gg << endl;      // gg is 26.
   // gg = 26
   cout << ++gg << endl;    // ggia is immidiately 27
   cout << gg << endl;      // ggia is 27

   return;
}

Link: Περισσότερα για την διαφορά prefix/suffix.