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  1. #include <type_traits>
  2. #include <utility>
  3. #include <iostream>
  4.  
  5. template<typename... Ts>
  6. struct typelist
  7. {};
  8.  
  9. namespace impl
  10. {
  11.     struct sfinae_result{};
  12.  
  13.     template<typename F , typename ARGS , typename ENABLED = sfinae_result>
  14.     struct is_valid_call;
  15.  
  16.     template<typename F , typename... ARGS>
  17.     struct is_valid_call<F,typelist<ARGS...>,
  18.                          decltype( std::declval<F>()(std::declval<ARGS>()...) )
  19.                         > : 
  20.         public std::true_type
  21.     {};
  22.  
  23.     template<typename F , typename... ARGS>
  24.     struct is_valid_call<F,typelist<ARGS...>,sfinae_result> : 
  25.         public std::false_type
  26.     {};
  27. }
  28.  
  29. template<typename F , typename... ARGS>
  30. struct is_valid_call : public impl::is_valid_call<F,typelist<ARGS...>>
  31. {};
  32.  
  33. void foo( int ){}
  34.  
  35. struct bar 
  36. {};
  37.  
  38. constexpr const bool ok   = is_valid_call<decltype(foo),int>::value;
  39. constexpr const bool nook = is_valid_call<decltype(foo),bar>::value;
  40.  
  41. int main()
  42. {
  43. 	std::cout << std::boolalpha;
  44. 	std::cout << "ok: " << ok << std::endl;
  45. 	std::cout << "nook: " << ok << std::endl;
  46. }
Success #stdin #stdout 0s 3296KB
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Standard input is empty
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ok: false
nook: false
https://ideone.com/yuXO8R
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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