Материал из C\C++ эксперт
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+ is overloaded using friend function
#include <iostream>
using namespace std;
class Point {
int x, y;
public:
Point() {} // needed to construct temporaries
Point(int px, int py) {
x = px;
y = py;
}
void show() {
cout << x << " ";
cout << y << "\n";
}
friend Point operator+(Point op1, Point op2); // now a friend
Point operator-(Point op2);
Point operator=(Point op2);
Point operator++();
};
// Now, + is overloaded using friend function.
Point operator+(Point op1, Point op2)
{
Point temp;
temp.x = op1.x + op2.x;
temp.y = op1.y + op2.y;
return temp;
}
// Overload - for Point.
Point Point::operator-(Point op2)
{
Point temp;
// notice order of operands
temp.x = x - op2.x;
temp.y = y - op2.y;
return temp;
}
// Overload assignment for Point.
Point Point::operator=(Point op2)
{
x = op2.x;
y = op2.y;
return *this; // i.e., return object that generated call
}
// Overload ++ for Point.
Point Point::operator++()
{
x++;
y++;
return *this;
}
int main()
{
Point ob1(10, 20), ob2( 5, 30);
ob1 = ob1 + ob2;
ob1.show();
return 0;
}15 50
Make op-- a friend; use reference
#include <iostream>
using namespace std;
class Point {
int x, y;
public:
Point() {}
Point(int px, int py) {
x = px;
y = py;
}
void show() {
cout << x << " ";
cout << y << "\n";
}
Point operator=(Point op2);
friend Point operator++(Point &op);
friend Point operator--(Point &op);
};
// Overload assignment for Point.
Point Point::operator=(Point op2)
{
x = op2.x;
y = op2.y;
return *this; // i.e., return object that generated call
}
// Now a friend; use a reference parameter.
Point operator++(Point &op)
{
op.x++;
op.y++;
return op;
}
// Make op-- a friend; use reference.
Point operator--(Point &op)
{
op.x--;
op.y--;
return op;
}
int main()
{
Point ob1(10, 20), ob2;
ob1.show();
++ob1;
ob1.show(); // displays 11 21
ob2 = ++ob1;
ob2.show(); // displays 12 22
--ob2;
ob2.show(); // displays 11 21
return 0;
}10 20
11 21
12 22
11 21
