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  1. #include <iostream>
  2. class Animal {
  3.  protected:
  4.   int a;
  5.  public:
  6.   friend void Swap(Animal &A,Animal &B);
  7.   int GetA() const { return a; }
  8. };
  9.  
  10. void Swap(Animal &A, Animal &B) {
  11.   int i = A.a;
  12.   A.a = B.a;
  13.   B.a = i;
  14. }
  15.  
  16. class People : public Animal
  17. {
  18.   public:
  19.     People() {
  20.       a = 1;
  21.     }
  22. };
  23.  
  24. class Fish : public Animal
  25. {
  26.   public:
  27.     Fish() {
  28.       a = 2;
  29.     }
  30. };
  31.  
  32. Animal *gA, *gB;
  33.  
  34. int main() {
  35.   gA = new People;
  36.   gB = new Fish;
  37.   std::cout << gA->GetA() << ", " << gB->GetA() << std::endl;;
  38.   Swap(*gA, *gB);
  39.   std::cout << gA->GetA() << ", " << gB->GetA() << std::endl;
  40.   return 0;
  41. }
  42.  
Success #stdin #stdout 0s 3472KB
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https://ideone.com/vgXoXy
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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