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  1. #include <iostream>
  2. #include <string>
  3.  
  4. using namespace std;
  5.  
  6.  
  7. class Thing {
  8. 	int a;
  9. public:
  10.     Thing(int v = 0): a (v) {}
  11. 	virtual const char * type_name(){ return "Thing"; }
  12. 	virtual int value() { return a; }
  13. };
  14.  
  15. class OtherThing : public Thing {
  16. public:
  17. 	OtherThing(int v): Thing(v) {}
  18. 	OtherThing() {}
  19.  
  20. 	virtual const char * type_name() { return "Other Thing"; }
  21. };
  22.  
  23. template <typename TO_T>
  24. inline TO_T* turn_thing_to(Thing* p) 
  25. {
  26.   return ::new(p) TO_T(static_cast<TO_T&&>(*p)); 
  27. }
  28.  
  29. int main() {
  30. 	Thing * thing = new Thing(42);
  31. 	std::cout << thing->type_name() << "\n";
  32. 	std::cout << thing->value() << "\n";
  33.  
  34. 	turn_thing_to<OtherThing>(thing);
  35. 	std::cout << thing->type_name() << "\n";
  36. 	std::cout << thing->value() << "\n";
  37. 	return 0;
  38. }
Success #stdin #stdout 0s 3472KB
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stdin
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Standard input is empty
stdout
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Thing
42
Other Thing
42
https://ideone.com/g1x6ng
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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