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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 
Standard input is empty
stdout 
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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