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  1. #include <iostream>
  2. using namespace std;
  3. template <typename T>
  4. class SmartPtr {
  5. public:
  6.   SmartPtr(T* ptr = 0) : pointee(ptr) {}
  7.   SmartPtr(SmartPtr& rhs) {
  8.     pointee = rhs.pointee;
  9. 	rhs.pointee = 0;
  10.   }
  11.   SmartPtr<T>& operator=(SmartPtr<T>& rhs) {
  12.   	if(this == &rhs)
  13.   	  return *this;
  14. 	  pointee = rhs.pointee;
  15. 	  rhs.pointee = 0;
  16.   }
  17.   ~SmartPtr() { delete pointee; }
  18.   //operator->, etc. irrelevant here.
  19.   //member template for type conversion
  20.   template <typename NewType>
  21.   operator SmartPtr<NewType>() {
  22.   	return SmartPtr<NewType>(pointee);
  23.   }
  24. private:
  25.   T* pointee;
  26. };
  27. class Remote {};
  28. class Base : public Remote {};
  29. class Derived : public Base {};
  30. void foo(const SmartPtr<Remote>& p) { cout << "remote" << endl;}
  31. void foo(const SmartPtr<Base>& p) { cout << "base" << endl;}
  32. template <>
  33. class SmartPtr<Base> {
  34. public:
  35. 	SmartPtr(Derived* p) : pointee(static_cast<Base*>(p)){}
  36. private:
  37.     Base* pointee;
  38. };
  39. int main() {
  40.     SmartPtr<Derived> d(new Derived());
  41.     //foo(d); //ambiguous call. How to remove ambiguity?
  42.     foo(static_cast<SmartPtr<Base>>(d)); //does not compile either.
  43.     return 0;
  44. }
Success #stdin #stdout 0s 3468KB
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https://ideone.com/aKq6C0
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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