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  1. #include <iostream>
  2.  
  3. class any {
  4. public:
  5.   template<class T>
  6.   any(T const& i) : _erasure() {
  7.     _erasure = new derive<T>(i);
  8.   }
  9.   any() = default;
  10.  
  11.   template<class T>
  12.   any& operator=(T const& i) {
  13.     if(_erasure) {
  14.       delete _erasure;
  15.     }
  16.     _erasure = new derive<T>(i);
  17.     return *this;
  18.   }
  19.  
  20.   void call() const { 
  21.     _erasure->call();
  22.   }
  23.  
  24. private:
  25.   struct base {
  26.     virtual ~base() {};
  27.     virtual void call() =0;
  28.   };
  29.  
  30.   template<class U>
  31.   struct derive : public base{
  32.     U val;
  33.     derive(U const& i) : val(i) {};
  34.     void call() {
  35.       val.call();
  36.     }
  37.   };
  38.  
  39.   base* _erasure;
  40. };
  41.  
  42. struct hoge {
  43.   void call() const { std::cout << "hoge::call" << std::endl; }
  44. };
  45.  
  46. struct foo {
  47.   void call() const { std::cout << "foo::call" << std::endl; }
  48. };
  49.  
  50. int main() {
  51.   any val;
  52.  
  53.   val = hoge();
  54.   val.call();
  55.  
  56.   val = foo();
  57.   val.call();
  58. }
Success #stdin #stdout 0s 2960KB
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Standard input is empty
stdout
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hoge::call
foo::call
https://ideone.com/3Z8Lr
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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