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  1. #include <iostream>
  2. using namespace std;
  3.  
  4.  
  5. template <typename T>
  6. struct NonConst {typedef T type;};
  7. template <typename T>
  8. struct NonConst<T const> {typedef T type;}; //by value
  9. template <typename T>
  10. struct NonConst<T const&> {typedef T& type;}; //by reference
  11. template <typename T>
  12. struct NonConst<T const*> {typedef T* type;}; //by pointer
  13. template <typename T>
  14. struct NonConst<T const&&> {typedef T&& type;}; //by rvalue-reference
  15.  
  16. template<typename TConstReturn, class TObj, typename... TArgs>
  17. typename NonConst<TConstReturn>::type likeConstVersion(
  18.    TObj const* obj,
  19.    TConstReturn (TObj::* memFun)(TArgs...) const,
  20.    TArgs... args) {
  21.       return const_cast<typename NonConst<TConstReturn>::type>(
  22.          (obj->*memFun)(args...));
  23. }
  24.  
  25. struct T {
  26.    int arr[100];
  27.    int const& getElement(size_t i) const{
  28.       return arr[i];
  29.    }
  30.    int& getElement(size_t i) {
  31.       return likeConstVersion(this, &T::getElement, i);
  32.    }
  33.    /*
  34.    int const& getElement() const{
  35.       return 42;
  36.    }
  37.    int& getElement() {
  38.       return likeConstVersion(this, &T::getElement);
  39.    }*/
  40. };
  41.  
  42. int main() {
  43. 	T t;  
  44. 	int b=t.getElement(4);
  45. 	return 0;
  46. }
Success #stdin #stdout 0s 15240KB
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stdout 
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https://ideone.com/fwqmsB
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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