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  1. #include <iostream>
  2. #include <utility>
  3. #include <vector>
  4.  
  5.     template<class E, E...es>
  6.     struct elements:std::integral_constant<unsigned, sizeof...(es)> { using type=E; };
  7.  
  8.     template<class E, E e0, E e1, E... es>
  9.     constexpr E next_helper( elements<E, e0, e1, es...>, E e, E first ) {
  10.       return (e0 == e)?e1:next_helper( elements<E, e1, es...>{}, e, first );
  11.     }
  12.     template<class E, E e0>
  13.     constexpr E next_helper( elements<E, e0>, E e, E first ) {
  14.       return first;
  15.     }
  16.     template<class E, E e0, E... es>
  17.     constexpr E next_helper( elements<E, e0, es...>, E e ) {
  18.       return next_helper( elements<E, e0, es...>{}, e, e0 );
  19.     }
  20.     template<class elements, class E>
  21.     constexpr E next( E e ) {
  22.       return next_helper( elements{}, e );
  23.     }
  24.     template<class elements, class E>
  25.     constexpr E next( E e, unsigned N );
  26.     template<class E, E...es>
  27.     constexpr E next_helper( elements<E,es...>, E e, unsigned N ) {
  28.       return (N>=sizeof...(es))?next<elements>( e, (N%sizeof...(es)) ):next<elements>( next<elements>( e, (N)/2 ), (N+1)/2 );
  29.     }
  30.     template<class elements, class E>
  31.     constexpr E next( E e, unsigned N ) {
  32.       return (N==0)?e:(N==1)?next<elements>(e):next_helper<elements>( next_helper<elements>( N/2, e ), (N+1)/2 );
  33.     }
  34.     template<class E, E e0, E e1, E... es>
  35.     constexpr unsigned index_helper( elements<E, e0, e1, es...>, E e ) {
  36.       return (e0==e)?0:(index_helper( elements<E, e1, es...>{}, e )+1);
  37.     }
  38.     template<class E, E e0>
  39.     constexpr unsigned index_helper( elements<E, e0>, E e ) {
  40.       return 0;
  41.     }
  42.     template<class elements, class E>
  43.     constexpr unsigned index( E e ) {
  44.       return index_helper( elements{}, e );
  45.     }
  46.     template<class E, E e0, E... es>
  47.     constexpr unsigned first_helper(elements<E, e0, es...>) {
  48.       return e0;
  49.     }
  50.     template<class elements>
  51.     constexpr auto first() -> typename elements::type {
  52.       return first_helper(elements{});
  53.     }
  54.     template<class elements>
  55.     constexpr auto nth(unsigned n) -> typename elements::type {
  56.       return next<elements>( first<elements>(), n );
  57.     }
  58.  
  59.     template<typename elements>
  60.     struct iteration_tuple {
  61.       using value_type = typename elements::type;
  62.       std::vector<value_type> data;
  63.       bool advance() {
  64.         bool finished = true;
  65.         for( value_type& e : data ) {
  66.           if ( first<elements>() != ( e = next<elements>(e) ) )
  67.             finished = false;
  68.           if (!finished)
  69.             break;
  70.         }
  71.         return finished;
  72.       }
  73.       iteration_tuple( unsigned size ) {
  74.         data.resize( size, first<elements>() );
  75.       }
  76.     };
  77.  
  78.     int main() {
  79.       typedef elements<int, -1, 0, 1> sequence;
  80.       iteration_tuple<sequence> sample(3);
  81.       do {
  82.         for (int x:sample.data)
  83.           std::cout << x << ",";
  84.         std::cout << "\n";
  85.       } while(!sample.advance());
  86.     }
  87.  
Success #stdin #stdout 0s 3472KB
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stdin
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Standard input is empty
stdout
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-1,-1,-1,
0,-1,-1,
1,-1,-1,
-1,0,-1,
0,0,-1,
1,0,-1,
-1,1,-1,
0,1,-1,
1,1,-1,
-1,-1,0,
0,-1,0,
1,-1,0,
-1,0,0,
0,0,0,
1,0,0,
-1,1,0,
0,1,0,
1,1,0,
-1,-1,1,
0,-1,1,
1,-1,1,
-1,0,1,
0,0,1,
1,0,1,
-1,1,1,
0,1,1,
1,1,1,
https://ideone.com/qtavHc
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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