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  1. #include <array>
  2. #include <type_traits>
  3.  
  4. template<int ... N>
  5. struct seq
  6. {
  7.    using type = seq<N...>;
  8.    static const std::size_t size = sizeof ... (N);
  9.  
  10.    template<int I>
  11.    struct push_back : seq<N..., I> {};
  12. };
  13.  
  14. template<int N>
  15. struct genseq : genseq<N-1>::type::template push_back<N-1> {};
  16.  
  17. template<>
  18. struct genseq<0> : seq<> {};
  19.  
  20. template<int N>
  21. using genseq_t = typename genseq<N>::type;
  22.  
  23. template<typename T, int...N>
  24. auto repeat(T value, seq<N...>) -> std::array<T, sizeof...(N)> 
  25. {
  26.    //unpack N, repeating `value` sizeof...(N) times
  27.    //note that (X, value) evaluates to value
  28.    return {(N, value)...}; 
  29. }
  30.  
  31. struct A{
  32.   A(int){}  
  33. };
  34.  
  35.  
  36. template<typename T, size_t N>
  37. std::array<T, N> filled_array(T const& u)
  38. {
  39.     //genseq_t<N> is seq<0,1,...N-1>
  40.     std::array<T, N> items = repeat(u, genseq_t<N>{} );
  41.     return items;
  42. }
  43.  
  44. int main() {
  45.     auto x = filled_array<A, 5>(A(1));
  46. }
Success #stdin #stdout 0s 3292KB
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https://ideone.com/srJGAL
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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