Mega Code Archive
Class pointer and virtual function
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#include <iostream>
using namespace std;
class figure {
protected:
double x, y;
public:
void set_dim(double i, double j=0) {
x = i;
y = j;
}
virtual void show_area() {
cout << "No area computation defined ";
cout << "for this class.\n";
}
} ;
class triangle : public figure {
public:
void show_area() {
cout << "Triangle with height ";
cout << x << " and base " << y;
cout << " has an area of ";
cout << x * 0.5 * y << ".\n";
}
};
class rectangle : public figure {
public:
void show_area() {
cout << "Rectangle with dimensions ";
cout << x << "x" << y;
cout << " has an area of ";
cout << x * y << ".\n";
}
};
class circle : public figure {
public:
void show_area() {
cout << "Circle with radius ";
cout << x;
cout << " has an area of ";
cout << 3.14 * x * x << ".\n";
}
} ;
int main()
{
figure *p; // create a pointer to base type
triangle t; // create objects of derived types
rectangle s;
circle c;
p = &t;
p->set_dim(10.0, 5.0);
p->show_area();
p = &s;
p->set_dim(10.0, 5.0);
p->show_area();
p = &c;
p->set_dim(9.0);
p->show_area();
return 0;
}
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