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  1.     template<typename E, E f, E...>
  2.     struct First
  3.     {
  4.         static const E value = f;
  5.     };
  6.  
  7.     template<typename E, E first, E head, E...>
  8.     struct Advance
  9.     {
  10.         static void adv(E& v)
  11.         {
  12.             if(v == head)
  13.                 v = first;
  14.         }
  15.     };
  16.  
  17.     template<typename E, E first, E head, E next, E... tail>
  18.     struct Advance<E,first,head,next,tail...>
  19.     {
  20.         static void adv(E& v)
  21.         {
  22.             if(v == head)
  23.                 v = next;
  24.             else
  25.                 Advance<E,first,next,tail...>::adv(v);
  26.         }
  27.     };
  28.  
  29.     template<typename E, E... values>
  30.     struct EnumValues
  31.     {
  32.         static void advance(E& v)
  33.         {
  34.             Advance<E, First<E, values...>::value, values...>::adv(v);
  35.         }
  36.     };
  37.  
  38.  
  39.     /// Test enum
  40.     enum class Fruit
  41.     {
  42.         apple,
  43.         banana,
  44.         orange,
  45.         pineapple,
  46.         lemon
  47.     };
  48.  
  49.     /// Scalable way, C++11-ish
  50.     typedef EnumValues<Fruit,
  51.             Fruit::apple,
  52.             Fruit::banana,
  53.             Fruit::orange,
  54.             Fruit::pineapple,
  55.             Fruit::lemon
  56.     > Fruit_values11;
  57.  
  58.     Fruit& operator++(Fruit& f)
  59.     {
  60.         Fruit_values11::advance(f);
  61.         return f;
  62.     }
  63.  
  64.  
  65.     #include <iostream>
  66.     std::ostream& operator<<(std::ostream& os, Fruit f)
  67.     {
  68.         switch(f)
  69.         {
  70.             case Fruit::apple: os << "Fruit::apple"; return os;
  71.             case Fruit::banana: os << "Fruit::banana"; return os;
  72.             case Fruit::orange: os << "Fruit::orange"; return os;
  73.             case Fruit::pineapple: os << "Fruit::pineapple"; return os;
  74.             case Fruit::lemon: os << "Fruit::lemon"; return os;
  75.         }
  76.     }
  77.  
  78.     int main()
  79.     {
  80.         Fruit f = Fruit::banana;
  81.         std::cout << "f = " << f << ";\n";
  82.         std::cout << "++f = " << ++f << ";\n";
  83.     }
Success #stdin #stdout 0s 2852KB
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f = Fruit::banana;
++f = Fruit::orange;
https://ideone.com/1o91Fl
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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