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  1. #include <tuple>
  2. #include <iostream>
  3. #include <functional>
  4.  
  5. template<int ...> struct seq {};
  6.  
  7. template<int N, int ...S> struct gens : gens<N-1, N-1, S...> {};
  8.  
  9. template<int ...S> struct gens<0, S...>{ typedef seq<S...> type; };
  10.  
  11. template <typename R, typename Tp, typename ...FArgs> 
  12. struct t_app_aux {
  13.   template<int ...S>
  14.   R static callFunc(std::function<R (FArgs...)> f,Tp t,seq<S...>) {
  15.     return f(std::get<S>(t) ...);
  16.   }
  17. };
  18.  
  19. template <typename R, typename Tp, typename ...FArgs>
  20. R t_app(std::function<R (FArgs...)> f, Tp t) {
  21.   static_assert(std::tuple_size<Tp>::value == sizeof...(FArgs), "type error: t_app wrong arity");
  22.   return t_app_aux<R, Tp, FArgs...>::callFunc(f,t,typename gens<sizeof...(FArgs)>::type());
  23. }
  24.  
  25.  
  26. struct foo
  27. {
  28.   foo() : _value(0) { std::cout << "default foo" << std::endl; }
  29.   foo(int value) : _value(value) { std::cout << "int foo" << std::endl; }
  30.   foo(const foo& other) : _value(other._value) { std::cout << "copy foo" << std::endl; }
  31.   foo(foo&& other) : _value(other._value) { std::cout << "move foo" << std::endl; }
  32.  
  33.   int _value;
  34. };
  35.  
  36. int main(void)
  37. {
  38.   std::cout << "Tuple creation" << std::endl;
  39.   std::tuple<int, float, foo> t = std::make_tuple(1, 1.2, foo(5));
  40.   std::cout << "Tuple created" << std::endl;
  41.   std::function<double (int,float,foo&)> foo1 = [](int x, float y, foo& z) {
  42.     return x + y + z._value;    
  43.   };
  44.  
  45.   std::cout << "Function created" << std::endl;
  46.   std::cout <<  t_app(foo1,t) << std::endl;
  47.   std::cout << "Function applied" << std::endl;
  48. }
Success #stdin #stdout 0s 3432KB
comments (?)
stdin
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Standard input is empty
stdout
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Tuple creation
int foo
move foo
move foo
Tuple created
Function created
copy foo
copy foo
7.2
Function applied
https://ideone.com/cAlorb
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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