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  1. #include <iostream>
  2. #include <cmath>
  3. #include <typeinfo>
  4. #include <exception>
  5. using namespace std;
  6.  
  7. using namespace std;
  8.  
  9. // Abstract base class.
  10. class Shape {
  11.  public:
  12.   // Virtual functions
  13.   virtual double area() { return 0; }
  14.   virtual double perimeter() { return 0; }
  15.   virtual void doubleArea() { /* do nothing */ }
  16.   virtual Shape* clone() const = 0;
  17.   virtual void copy(const Shape&r) = 0; 
  18. };
  19.  
  20. // Derived class.
  21. class Circle: public Shape {
  22.  private:
  23.   double radius;
  24.  
  25.  public:
  26.   Circle (double r) : radius(r) {}
  27.   double area() { return (M_PI*pow(radius,2)); }
  28.   double perimeter() { return (M_PI*2*radius); }
  29.   void doubleArea() { radius *= pow(2,0.5); }
  30.   Circle* clone() const { return new Circle(*this); }
  31.   void copy(const Shape&r) override {
  32.   	if (dynamic_cast<const Circle*>(&r)) 
  33.   	    *this = *dynamic_cast<const Circle*>(&r);
  34.   	else throw (invalid_argument("ouch! circle copy mismatch"));
  35.   }
  36.  
  37. };
  38.  
  39. void modShape(Shape &inShape) {
  40.  
  41.   // Make new Shape* from clone of inShape
  42.   // and double its area.
  43.   Shape* newShape = inShape.clone();
  44.   newShape->doubleArea();
  45.   cout << "newShape's area (after doubling): " << newShape->area() << endl;
  46.  
  47.   // Copy newShape to inShape.
  48.   inShape.copy(*newShape);
  49.   cout << "newShape copied to inShape (circ)." << endl;
  50.   cout << "inShape's area in modShape: " << inShape.area() << endl;
  51.  
  52. };
  53.  
  54.  
  55. int main() {
  56.  
  57.   Circle circ(2);
  58.   cout << "circ's initial area (in main): " << circ.area() << endl;
  59.   modShape(circ);
  60.   cout << "circ's final area (in main): " << circ.area() << endl;
  61.  
  62.   return 0;
  63. }
Success #stdin #stdout 0s 3416KB
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Standard input is empty
stdout
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circ's initial area (in main): 12.5664
newShape's area (after doubling): 25.1327
newShape copied to inShape (circ).
inShape's area in modShape: 25.1327
circ's final area (in main): 25.1327
https://ideone.com/gYfa15
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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