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  1. #include <iostream>
  2. #include <initializer_list>
  3. #include <array>
  4.  
  5. template <class T>
  6. struct EIV_t {
  7.   size_t i;
  8.   T      v;
  9. };
  10.  
  11. class EI_t {
  12. public:
  13.   EI_t(size_t i) : i(i) {}
  14.   template <class T>
  15.   EIV_t<T> operator = (const T& v) const
  16.   {
  17.      return EIV_t<T> { i, v };
  18.   }
  19. private:
  20.   size_t i;
  21. }; 
  22. class E_t {
  23. public:
  24.   EI_t operator [] (size_t i) const { return EI_t(i); }
  25. }; 
  26.  
  27. extern E_t E;
  28.  
  29. template <class T, size_t N>
  30. class CArray : private std::array<T,N> {
  31.   typedef std::array<T,N> Base;
  32. public:
  33.   CArray() : Base() {}
  34.   CArray(std::initializer_list<T> l) : Base(l) {}
  35.   CArray(std::initializer_list<EIV_t<T>> l) : Base() {
  36.      for (auto i = l.begin(); i != l.end(); ++i) {
  37.          (*this)[i->i] = i->v;
  38.      }
  39.   }
  40.  
  41.  
  42.   // well, private inheritance has its cost
  43.   using Base::operator [];
  44.   using Base::begin;
  45.   using Base::end;
  46.   using Base::cbegin;
  47.   using Base::cend;
  48.   using Base::iterator;
  49.   using Base::const_iterator;
  50.   // a lot of missing...
  51. };
  52.  
  53. E_t E;
  54.  
  55. int main() {
  56.    CArray<int, 7> a { E[1] = 13, E[6] = 14 };
  57.    for (auto i = a.begin(); i != a.end(); ++i) {
  58.       std::cout << *i << std::endl;
  59.    } 
  60. }
  61.  
Success #stdin #stdout 0s 2884KB
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stdin
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Standard input is empty
stdout
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0
13
0
0
0
0
14
https://ideone.com/nzWL0
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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