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  1. #include <iostream>
  2. #include <memory>
  3. #include <list>
  4.  
  5. class Base {
  6.     friend class BaseWrapper;
  7.     friend std::ostream & operator << (std::ostream &os, const Base &b) {
  8.         b.print(os);
  9.         return os;
  10.     }
  11.     virtual void print (std::ostream &os) const = 0;
  12.     virtual Base * clone () const = 0;
  13. protected:
  14.     template <typename T> static Base * clone_impl (const T &t) {
  15.         return new T(t);
  16.     }
  17. public:
  18.     virtual ~Base () {}
  19. };
  20.  
  21. class Derived1 : public Base {
  22.     std::string s;
  23.     void print (std::ostream &os) const { os << s; }
  24.     Base * clone () const { return clone_impl(*this); }
  25. public:
  26.     Derived1 () : s("D1") {}
  27. };
  28.  
  29. class Derived2 : public Base {
  30.     int x;
  31.     std::string s;
  32.     double y;
  33.     void print (std::ostream &os) const { os << (x + y) << ":" << s; }
  34.     Base * clone () const { return clone_impl(*this); }
  35. public:
  36.     Derived2 () : x(3), s("D2"), y(.14159) {}
  37. };
  38.  
  39. class Derived3 : public Base {
  40.     std::string s;
  41.     void print (std::ostream &os) const { os << s; }
  42.     Base * clone () const { return clone_impl(*this); }
  43. public:
  44.     Derived3 () : s("D3") {}
  45. };
  46.  
  47. class BaseWrapper : public Base {
  48.     std::unique_ptr<Base> ptr;
  49.     void print (std::ostream &os) const { ptr->print(os); }
  50.     Base * clone () const { return ptr->clone(); }
  51. public:
  52.     BaseWrapper (const Base &b) : ptr(b.clone()) {}
  53.     BaseWrapper (BaseWrapper &&b) { ptr.swap(b.ptr); }
  54. };
  55.  
  56. typedef std::list<BaseWrapper> any_list;
  57.  
  58. int main ()
  59. {
  60.     any_list l;
  61.     l.push_back(Derived1());
  62.     l.push_back(Derived2());
  63.     l.push_back(Derived3());
  64.  
  65.     for (const auto &x : l) {
  66.         std::cout << " " << x;
  67.     }
  68.     std::cout << std::endl;
  69. }
Success #stdin #stdout 0s 3032KB
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Standard input is empty
stdout
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 D1 3.14159:D2 D3
https://ideone.com/YXFq64
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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