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  1. //http://stackoverflow.com/questions/27433533/making-template-from-any-parameter-a-friend-to-template-with-one-parameter-c/27436693#27436693
  2.  
  3.  
  4. #include <type_traits>
  5. #include <memory>
  6. #include <iostream>
  7.  
  8. template<typename T, typename U>
  9. struct is_non_class_same : public std::integral_constant<bool, (!std::is_base_of<
  10.         typename std::remove_pointer<T>::type,
  11.         typename std::remove_pointer<U>::type>::value &&
  12.         std::is_convertible<U, T>::value && sizeof(T) >= sizeof(U)) ||
  13. (std::is_class<T>::value && std::is_class<U>::value &&
  14.  !std::is_pointer<T>::value && !std::is_pointer<U>::value &&
  15.  std::is_same<T, U>::value)>
  16. {};
  17.  
  18. template<typename T, typename U>
  19. struct is_class_same : public std::integral_constant<bool, std::is_base_of<
  20.         typename std::remove_pointer<T>::type,
  21.         typename std::remove_pointer<U>::type>::value &&
  22.         std::is_pointer<T>::value>
  23. {};
  24.  
  25.  
  26. class Node
  27. {
  28. protected:
  29.     Node* previous;
  30.     Node* next;
  31.  
  32.     Node() : previous(nullptr), next(nullptr) {}
  33.  
  34.     template<class T, class TD>
  35.     friend class linked_ptr;
  36.  
  37. public:
  38.     virtual ~Node() {}
  39.  
  40. };
  41.  
  42. template<typename T, typename TD = typename std::remove_pointer<T>::type>
  43. class linked_ptr : public Node
  44. {
  45. private:
  46.     template<class, class> friend class linked_ptr; /** Access friend level **/
  47.     T data;
  48.  
  49. public:
  50.  
  51.     template<class U, typename TU = typename std::remove_pointer<U>::type, typename = typename std::enable_if<is_non_class_same<T, U>::value || is_class_same<T, U>::value, U>::type>
  52.     linked_ptr(U data) : data(data) {}
  53.     ~linked_ptr();
  54.  
  55.     template<class U, typename TU = typename std::remove_pointer<U>::type, typename = typename std::enable_if<is_non_class_same<T, U>::value || is_class_same<T, U>::value, U>::type>
  56.     void setData(U data)
  57.     {
  58.         this->data = data;
  59.     }
  60.  
  61.     template<class U, typename TU = typename std::remove_pointer<U>::type, typename = typename std::enable_if<is_non_class_same<T, U>::value || is_class_same<T, U>::value, U>::type>
  62.     void append(U data);
  63. };
  64.  
  65. template<typename T, typename TD>
  66. linked_ptr<T, TD>::~linked_ptr()
  67. {
  68.     TD(data);
  69.     delete this->next;
  70. }
  71.  
  72. template<typename T, typename TD>
  73. template<typename U, typename TU, class>
  74. void linked_ptr<T, TD>::append(U data)
  75. {
  76.     if (!this->next)
  77.     {
  78.         this->next = new linked_ptr<U, TU>(data);
  79.         this->next->previous = this;
  80.         return;
  81.     }
  82.  
  83.     Node* t = this->next;
  84.     while(t->next != nullptr)
  85.     {
  86.         t = t->next;
  87.     }
  88.  
  89.     t->next = new linked_ptr<U, TU>(data);
  90. }
  91.  
  92.  
  93.  
  94.  
  95. class foo
  96. {
  97. public:
  98.     virtual ~foo()
  99.     {
  100.         std::cout<<"destroyed foo\n";
  101.     };
  102.  
  103.     virtual void print()
  104.     {
  105.         std::cout<<"foo\n";
  106.     }
  107. };
  108.  
  109. class bar : public foo
  110. {
  111. public:
  112.     virtual ~bar()
  113.     {
  114.         std::cout<<"destroyed bar\n";
  115.     }
  116.  
  117.     virtual void print()
  118.     {
  119.         std::cout<<"bar\n";
  120.     }
  121. };
  122.  
  123. int main()
  124. {
  125.     linked_ptr<foo*> list(new foo());
  126.     list.append(new bar());
  127.     list.append(new bar());
  128.     list.append(new bar());
  129. }
Success #stdin #stdout 0s 3432KB
comments (?)
stdin
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Standard input is empty
stdout
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destroyed bar
destroyed foo
destroyed bar
destroyed foo
destroyed bar
destroyed foo
destroyed foo
https://ideone.com/dHZhHc
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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