fork download
copy 
  1. #include <type_traits>
  2.  
  3.     template<typename Func, typename Arg, typename Enable = void>
  4.     struct has_call_with_arg1 : public std::false_type {};
  5.  
  6.     template<typename Func, typename Arg>
  7.     struct has_call_with_arg1<Func, Arg,
  8.         decltype(std::declval<Func&>()(std::declval<Arg&>()))>
  9.         : public std::true_type {};
  10.  
  11.     namespace has_call_with_arg_impl {
  12.         template<typename F, typename A>
  13.         std::true_type test(decltype(std::declval<F&>()(std::declval<A&>()))*);
  14.  
  15.         template<typename F, typename A>
  16.         std::false_type test(...);
  17.     }
  18.  
  19.     template <typename Func, typename Arg>
  20.     struct has_call_with_arg2
  21.         : public decltype(has_call_with_arg_impl::test<Func,Arg>(nullptr)) {};
  22.  
  23. struct X {};
  24. struct Y {
  25.     void operator()(X);
  26. };
  27.  
  28. int main() {
  29.     static_assert(has_call_with_arg1<void(int), int>::value, "Line 1");
  30.     static_assert(has_call_with_arg1<Y, X>::value, "Line 2");
  31.     static_assert(!has_call_with_arg1<Y, int>::value, "Line 3");
  32.     static_assert(has_call_with_arg2<void(int), int>::value, "Line 4");
  33.     static_assert(has_call_with_arg2<Y, X>::value, "Line 5");
  34.     static_assert(!has_call_with_arg2<Y, int>::value, "Line 6");
  35. }
Success #stdin #stdout 0s 2892KB
comments ()
stdin
copy 
Standard input is empty
stdout
copy 
Standard output is empty
https://ideone.com/KgRI8y
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
secret

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!