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  1. #include <iostream>
  2. #include <vector>
  3. #include <memory>
  4. #include <typeinfo>
  5.  
  6. class Any {
  7.     struct Base {
  8.         virtual ~Base () {}
  9.         virtual std::ostream & output (std::ostream &) const = 0;
  10.     };
  11.     template <typename T>
  12.     struct Impl : Base {
  13.         T value_;
  14.         explicit Impl (T x) : value_(x) {}
  15.         operator T () const { return value_; }
  16.         std::ostream & output (std::ostream &os) const { return os << value_; }
  17.     };
  18.     std::shared_ptr<const Base> base_ptr_;
  19. public:
  20.     Any () : base_ptr_() {}
  21.     template <typename T> Any (T x) : base_ptr_(new Impl<T>(x)) {}
  22.     template <typename T> operator T () const {
  23.         return dynamic_cast<const Impl<T> &>(*base_ptr_.get());
  24.     }
  25.     friend std::ostream & operator << (std::ostream &os, const Any &a) {
  26.         return a.base_ptr_->output(os);
  27.     }
  28. };
  29.  
  30. int main () {
  31.     std::vector<Any> v;
  32.  
  33.     // insert heterogeneous data
  34.     v.push_back(1);
  35.     v.push_back("two");
  36.     v.push_back(3.14F);
  37.     v.push_back('4');
  38.  
  39.     // demonstrate printing
  40.     for (auto i = v.begin(); i != v.end(); ++i) {
  41.         std::cout << *i << std::endl;
  42.     }
  43.  
  44.     // demonstrate type introspection
  45.     for (auto i = v.begin(); i != v.end(); ++i) {
  46.         try { static_cast<int>(*i); std::cout << *i << " is int\n"; }
  47.         catch (std::bad_cast) {}
  48.         try { static_cast<const char *>(*i); std::cout << *i << " is c_str\n"; }
  49.         catch (std::bad_cast) {}
  50.         try { static_cast<float>(*i); std::cout << *i << " is float\n"; }
  51.         catch (std::bad_cast) {}
  52.         try { static_cast<char>(*i); std::cout << *i << " is char\n"; }
  53.         catch (std::bad_cast) {}
  54.     }
  55. }
Success #stdin #stdout 0s 3480KB
comments (?)
stdin
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Standard input is empty
stdout
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1
two
3.14
4
1 is int
two is c_str
3.14 is float
4 is char
https://ideone.com/IonCML
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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