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  1.  
  2.     template<typename E, E first, E head>
  3.     void advanceEnum(E& v)
  4.     {
  5.         if(v == head)
  6.             v = first;
  7.     }
  8.  
  9.     template<typename E, E first, E head, E next, E... tail>
  10.     void advanceEnum(E& v)
  11.     {
  12.         if(v == head)
  13.             v = next;
  14.         else
  15.             advanceEnum<E,first,next,tail...>(v);
  16.     }
  17.  
  18.     template<typename E, E first, E... values>
  19.     struct EnumValues
  20.     {
  21.         static void advance(E& v)
  22.         {
  23.             advanceEnum<E, first, first, values...>(v);
  24.         }
  25.     };
  26.  
  27.  
  28.  
  29.     /// Test enum
  30.     enum class Fruit
  31.     {
  32.         apple,
  33.         banana,
  34.         orange,
  35.         pineapple,
  36.         lemon
  37.     };
  38.  
  39.  
  40.  
  41.     /// Scalable way, C++11-ish
  42.     typedef EnumValues<Fruit,
  43.             Fruit::apple,
  44.             Fruit::banana,
  45.             Fruit::orange,
  46.             Fruit::pineapple,
  47.             Fruit::lemon
  48.     > Fruit_values11;
  49.  
  50.     Fruit& operator++(Fruit& f)
  51.     {
  52.         Fruit_values11::advance(f);
  53.         return f;
  54.     }
  55.  
  56.  
  57.     #include <iostream>
  58.     std::ostream& operator<<(std::ostream& os, Fruit f)
  59.     {
  60.         switch(f)
  61.         {
  62.             case Fruit::apple: os << "Fruit::apple"; return os;
  63.             case Fruit::banana: os << "Fruit::banana"; return os;
  64.             case Fruit::orange: os << "Fruit::orange"; return os;
  65.             case Fruit::pineapple: os << "Fruit::pineapple"; return os;
  66.             case Fruit::lemon: os << "Fruit::lemon"; return os;
  67.         }
  68.     }
  69.  
  70.     int main()
  71.     {
  72.         Fruit f = Fruit::banana;
  73.         std::cout << "f = " << f << ";\n";
  74.         std::cout << "++f = " << ++f << ";\n";
  75.         std::cout << "++f = " << ++f << ";\n";
  76.         std::cout << "++f = " << ++f << ";\n";
  77.         std::cout << "++f = " << ++f << ";\n";
  78.         std::cout << "++f = " << ++f << ";\n";
  79.     }
Success #stdin #stdout 0s 2896KB
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stdin
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Standard input is empty
stdout
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f = Fruit::banana;
++f = Fruit::orange;
++f = Fruit::pineapple;
++f = Fruit::lemon;
++f = Fruit::apple;
++f = Fruit::banana;
https://ideone.com/Htlg0G
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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