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  1. #include <tuple>
  2. #include <iostream>
  3. #include <functional>
  4. #include <type_traits>
  5.  
  6.  
  7. struct foo
  8. {
  9.   foo() : _value(0) { std::cout << "default foo" << std::endl; }
  10.   foo(int value) : _value(value) { std::cout << "int foo" << std::endl; }
  11.   foo(const foo& other) : _value(other._value) { std::cout << "copy foo" << std::endl; }
  12.   foo(foo&& other) : _value(other._value) { std::cout << "move foo" << std::endl; }
  13.  
  14.   int _value;
  15. };
  16.  
  17. template<int ...> struct seq {};
  18.  
  19. template<int N, int ...S> struct gens : gens<N-1, N-1, S...> {};
  20.  
  21. template<int ...S> struct gens<0, S...>{ typedef seq<S...> type; };
  22.  
  23. template <typename R, typename Tp, typename ...FArgs> 
  24. struct t_app_aux {
  25.   template<int ...S>
  26.   R static callFunc(std::function<R (FArgs...)> f, Tp&& t, seq<S...>) {
  27.     return f(std::get<S>(std::forward<Tp>(t)) ...);
  28.   }
  29. };
  30.  
  31. template <typename R, typename Tp, typename ...FArgs>
  32. R t_app(std::function<R (FArgs...)> f, Tp&& t) 
  33. {
  34.  static_assert(std::tuple_size<typename std::remove_reference<Tp>::type>::value == sizeof...(FArgs), 
  35.                 "type error: t_app wrong arity");
  36.  
  37.   return t_app_aux<R, Tp, FArgs...>::callFunc(f, std::forward<Tp>(t), typename gens<sizeof...(FArgs)>::type());
  38. }
  39.  
  40.  
  41.  
  42. int main(void)
  43. {
  44.   std::cout << "Tuple creation" << std::endl;
  45.   std::tuple<int, float, foo> t = std::make_tuple(1, 1.2, foo(5));
  46.   std::cout << "Tuple created" << std::endl;
  47.   std::function<double (int,float,foo&)> foo1 = [](int x, float y, foo& z) {
  48.     return x + y + z._value;    
  49.   };
  50.  
  51.   std::cout << "Function created" << std::endl;
  52.   std::cout <<  t_app(foo1,t) << std::endl;
  53.   std::cout << "Function applied" << std::endl;
  54. }
Success #stdin #stdout 0s 3472KB
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
7.2
Function applied
https://ideone.com/S3wF6x
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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