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  1. #include <iostream>
  2. #include <type_traits>
  3. #include <string>
  4. #include <vector>
  5.  
  6. template<typename... T> class tuple;
  7. template<> class tuple<> {};
  8. template<typename H, typename... T>
  9. class tuple<H, T...> : private tuple<T...>
  10. {
  11.     typedef tuple<T...> inherited;
  12.  public:
  13.     tuple() {}
  14.     tuple(typename std::add_lvalue_reference<typename std::add_const<H>::type>::type v,
  15.           typename std::add_lvalue_reference<typename std::add_const<T>::type>::type... vtail)
  16.         : inherited(vtail...), m_head(v) { }
  17.     template<typename... VValues>
  18.     tuple(const tuple<VValues...>& other)
  19.         : inherited(other.tail()), m_head(other.head()) { }
  20.     template<typename... VValues>
  21.     tuple& operator=(const tuple<VValues...>& other)
  22.     {
  23.         m_head = other.head();
  24.         tail() = other.tail();
  25.         return *this;
  26.     }
  27.     typename std::add_lvalue_reference<H>::type head() { return m_head; }
  28.     typename std::add_lvalue_reference<const H>::type head() const { return m_head; }
  29.  
  30.     inherited& tail() { return *this; }
  31.     const inherited& tail() const { return *this; }
  32.  protected:
  33.      H m_head;
  34. };
  35.  
  36. template<class... T>
  37. tuple<T...> make_tuple(T&&... t)
  38. {
  39.     return tuple<T...>(t...);
  40. }
  41.  
  42. int main()
  43. {
  44.     tuple<std::string, std::vector<int>, double> tt("hello", {1,2,3,4}, 1.2);
  45.     std::string h = tt.head();
  46.     tuple<std::vector<int>, double> t2 = tt.tail();
  47.  
  48.     std::string s = "Hello";
  49.     std::vector<int> v = {1,22,3,4,5};
  50.     auto x = make_tuple(s, v, 1.2);
  51.  
  52.     std::cout << "tt.head is " << tt.head() << '\n'
  53.               << "t2.tail.head is " << t2.tail().head() << '\n'
  54.               << " x.head is " << x.head() << '\n';
  55. }
  56.  
Success #stdin #stdout 0s 2964KB
comments (?)
stdin 
Standard input is empty
stdout 
tt.head is hello
t2.tail.head is 1.2
 x.head is Hello
https://ideone.com/RyYrP
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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