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  1.     template<typename E, E v>
  2.     struct EnumValue
  3.     {
  4.         static const E value = v;
  5.     };
  6.  
  7.     template<typename h, typename t>
  8.     struct StaticList
  9.     {
  10.         typedef h head;
  11.         typedef t tail;
  12.     };
  13.  
  14.     template<typename list, typename first>
  15.     struct CyclicHead
  16.     {
  17.         typedef typename list::head item;
  18.     };
  19.  
  20.     template<typename first>
  21.     struct CyclicHead<void,first>
  22.     {
  23.         typedef first item;
  24.     };
  25.  
  26.     template<typename E, typename list, typename first = typename list::head>
  27.     struct Advance
  28.     {
  29.         typedef typename list::head lh;
  30.         typedef typename list::tail lt;
  31.         typedef typename CyclicHead<lt, first>::item next;
  32.  
  33.         static void advance(E& value)
  34.         {
  35.             if(value == lh::value)
  36.                 value = next::value;
  37.             else
  38.                 Advance<E, typename list::tail, first>::advance(value);
  39.         }
  40.     };
  41.  
  42.     template<typename E, typename f>
  43.     struct Advance<E,void,f>
  44.     {
  45.         static void advance(E& value)
  46.         {
  47.         }
  48.     };
  49.  
  50.     /// Test enum
  51.     enum class Fruit
  52.     {
  53.         apple,
  54.         banana,
  55.         orange,
  56.         pineapple,
  57.         lemon
  58.     };
  59.  
  60.     /// Scalable way, C++03-ish
  61.     typedef StaticList<EnumValue<Fruit,Fruit::apple>,
  62.             StaticList<EnumValue<Fruit,Fruit::banana>,
  63.             StaticList<EnumValue<Fruit,Fruit::orange>,
  64.             StaticList<EnumValue<Fruit,Fruit::pineapple>,
  65.             StaticList<EnumValue<Fruit,Fruit::lemon>,
  66.             void
  67.     > > > > > Fruit_values;
  68.  
  69.     Fruit& operator++(Fruit& f)
  70.     {
  71.         Advance<Fruit, Fruit_values>::advance(f);
  72.         return f;
  73.     }
  74.  
  75.  
  76.  
  77.     #include <iostream>
  78.     std::ostream& operator<<(std::ostream& os, Fruit f)
  79.     {
  80.         switch(f)
  81.         {
  82.             case Fruit::apple: os << "Fruit::apple"; return os;
  83.             case Fruit::banana: os << "Fruit::banana"; return os;
  84.             case Fruit::orange: os << "Fruit::orange"; return os;
  85.             case Fruit::pineapple: os << "Fruit::pineapple"; return os;
  86.             case Fruit::lemon: os << "Fruit::lemon"; return os;
  87.         }
  88.     }
  89.  
  90.     int main()
  91.     {
  92.         Fruit f = Fruit::banana;
  93.         std::cout << "f = " << f << ";\n";
  94.         std::cout << "++f = " << ++f << ";\n";
  95.     }
Success #stdin #stdout 0s 2852KB
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stdin
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Standard input is empty
stdout
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f = Fruit::banana;
++f = Fruit::orange;
https://ideone.com/SYfZKv
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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