fork download
copy 
  1. class Base {
  2.     virtual void dummy() = 0;
  3.     // this is to generate a vtable, but note there is no virtual f()
  4. };
  5.  
  6. class A : public Base {
  7. public:
  8.     void f() { /* ... */ };
  9.     void dummy() {};
  10. };
  11.  
  12. class B : public Base {
  13. public:
  14.     void f() { /* different implementation from A */ };
  15.     void dummy() {};
  16. };
  17.  
  18. template<class T1, class T2, class T3>
  19. void doStuff(T1 &x, T2 &y, T3 &z) {
  20.     for (int i=1; i<100000; ++i) {
  21.         x.f();
  22.         y.f();
  23.         z.f();
  24.     }
  25. }
  26.  
  27. void doStuff(Base &x, Base &y, Base &z) {
  28.     A *a_x = dynamic_cast<A*>(&x);
  29.     B *b_x = dynamic_cast<B*>(&x);
  30.     A *a_y = dynamic_cast<A*>(&y);
  31.     B *b_y = dynamic_cast<B*>(&y);
  32.     A *a_z = dynamic_cast<A*>(&z);
  33.     B *b_z = dynamic_cast<B*>(&z);
  34.     if (a_x && a_y && a_z) {
  35.         doStuff(*a_x, *a_y, *a_z);
  36.     } else if (a_x && a_y && b_z) {
  37.         doStuff(*a_x, *a_y, *b_z);
  38.     }
  39.     // ... and so on for all eight combinations of A and B.
  40. }
  41.  
  42. int main() {
  43.     Base *x = new A();
  44.     Base *y = new B();
  45.     Base *z = new A();
  46.  
  47.     doStuff(*x, *y, *z);
  48.     // oops - this instantiates to doStuff(Base &, Base &, Base &)
  49.     // and there's no Base::f().
  50. }
Success #stdin #stdout 0s 3468KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Standard output is empty
https://ideone.com/YzxE5q
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!