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  1.  
  2.     #include <cstddef>
  3.     #include <utility>
  4.     #include <vector>
  5.     #include <tuple>
  6.     #include <string>
  7.     #include <iostream>
  8.  
  9.     using std::size_t;
  10.  
  11.     template<size_t...> struct seq {};
  12.     template<size_t Min, size_t Max, size_t... s>
  13.     struct make_seq:make_seq< Min, Max-1, Max-1, s... > {};
  14.     template<size_t Min, size_t... s>
  15.     struct make_seq< Min, Min, s... > {
  16.         typedef seq<s...> type;
  17.     };
  18.     template<size_t Max, size_t Min=0>
  19.     using MakeSeq = typename make_seq<Min, Max>::type;
  20.  
  21.     size_t product_size() {
  22.       return 1;
  23.     }
  24.     template<typename... Sizes>
  25.     size_t product_size( size_t x, Sizes... tail ) {
  26.       return x * product_size(tail...);
  27.     }
  28.     namespace details {
  29.       template<typename max_iterator, typename Lambda>
  30.       void for_each_index( max_iterator mbegin, max_iterator mend, Lambda&& f, std::vector<size_t>& idx ) {
  31.         if (mbegin == mend) {
  32.           f(idx);
  33.         } else {
  34.           for (size_t i = 0; i < *mbegin; ++i) {
  35.             idx.push_back(i);
  36.             for_each_index(mbegin+1, mend, f, idx);
  37.             idx.pop_back();
  38.           }
  39.         }
  40.       }
  41.       template<typename Lambda>
  42.       void for_each_index( std::vector<size_t> const& maxes, Lambda&& f ) {
  43.         std::vector<size_t> idx;
  44.         details::for_each_index( maxes.begin(), maxes.end(), f, idx );
  45.       }
  46.       template<size_t... s, typename... Ts>
  47.       std::vector< std::tuple<Ts...> > does_it_blend( seq<s...>, std::tuple< std::vector<Ts>... >const& input ) {
  48.         std::vector< std::tuple<Ts...> > retval;
  49.         retval.reserve( product_size( std::get<s>(input).size()... ) );
  50.         std::vector<size_t> maxes = {
  51.           (std::get<s>(input).size())...
  52.         };
  53.         for_each_index( maxes, [&](std::vector<size_t> const& idx){
  54.           retval.emplace_back( std::get<s>(input)[idx[s]]... );
  55.         });
  56.         return retval;
  57.       }
  58.     }
  59.     template<typename... Ts>
  60.     std::vector< std::tuple<Ts...> > does_it_blend( std::tuple< std::vector<Ts>... >const& input ) {
  61.       return details::does_it_blend( MakeSeq< sizeof...(Ts) >(), input );
  62.     }
  63.  
  64.     int main() {
  65.       std::tuple< std::vector<int>, std::vector<bool>, std::vector<std::string> > input {
  66.         { 1, 2, 3}, { false, true}, { "Hello", "World"}
  67.       };
  68.  
  69.       // should become 3 x 2 x 2 = 12 cases { {1, false, "Hello"}, ... , {3, true, "World"} } 
  70.       std::vector< std::tuple<int, bool, std::string> > test_cases = does_it_blend( input );
  71.  
  72.       for( auto&& x:test_cases ) {
  73.         std::cout << std::get<0>(x) << "," << std::get<1>(x) << "," << std::get<2>(x) << "\n";
  74.       }
  75.     }
  76.  
  77.  
Success #stdin #stdout 0s 2992KB
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stdin
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Standard input is empty
stdout
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1,0,Hello
1,0,World
1,1,Hello
1,1,World
2,0,Hello
2,0,World
2,1,Hello
2,1,World
3,0,Hello
3,0,World
3,1,Hello
3,1,World
https://ideone.com/ThhAoa
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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