Use virtual functions and polymorphism. : polymorphism « Class « C++ Tutorial

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C++ Tutorial » Class » polymorphism 
9.29.1.Use virtual functions and polymorphism.
#include <iostream> 
#include <cstring> 
using namespace std; 
 
class Shape 
  double width; 
  double height; 
 
  char name[20]
public
  Shape() { 
    width = height = 0.0
    strcpy(name, "unknown")
  
 
  Shape(double w, double h, char *n) { 
    width = w; 
    height = h; 
    strcpy(name, n)
  
 
  Shape(double x, char *n) { 
    width = height = x; 
    strcpy(name, n)
  
 
  void display() { 
    cout << "Width and height are " << width << " and " << height << "\n"
  
 
  double getWidth() { return width; 
  double getHeight() { return height; 
  void setWidth(double w) { width = w; 
  void setHeight(double h) { height = h; 
  char *getName() { return name; 
 
  virtual double area() {   
    cout << "Error: area() must be overridden.\n";  
    return 0.0;  
  }   
 
}
 
class Triangle : public Shape 
  char style[20];
public
 
  Triangle() { 
    strcpy(style, "unknown")
  
 
  Triangle(char *str, double w, double h: Shape(w, h, "triangle") { 
    strcpy(style, str)
  
   
  Triangle(double x: Shape(x, "triangle") { 
    strcpy(style, "isosceles");  
  
 
  double area() { 
    return getWidth() * getHeight() 2
  
 
  void showStyle() { 
    cout << "Triangle is " << style << "\n"
  
}
 
class Rectangle : public Shape 
public
 
  Rectangle(double w, double h: Shape(w, h, "rectangle") { }  
  
  Rectangle(double x: Shape(x, "rectangle") { }  
 
  bool isSquare() { 
    if(getWidth() == getHeight()) 
       return true
    return false
  
 
  double area() { 
    return getWidth() * getHeight()
  
}
 
int main() { 
  Shape *shapes[5]
  
  shapes[0= &Triangle("right"8.012.0);  
  shapes[1= &Rectangle(10);  
  shapes[2= &Rectangle(104);  
  shapes[3= &Triangle(7.0);  
  shapes[4= &Shape(1020"generic")
  
  for(int i=0; i < 5; i++) {  
    cout << "object is " << shapes[i]->getName() << "\n";  
    cout << "Area is " << shapes[i]->area() << "\n\n";  
  }  
 
  return 0
}
object is generic
Error: area() must be overridden.
Area is 0

object is generic
Error: area() must be overridden.
Area is 0

object is generic
Error: area() must be overridden.
Area is 0

object is generic
Error: area() must be overridden.
Area is 0

object is generic
Error: area() must be overridden.
Area is 0
9.29.polymorphism
9.29.1.Use virtual functions and polymorphism.
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