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  1. #include <iostream>
  2.  
  3. struct P{};
  4.  
  5. struct S{bool operator()(){return true;}};
  6.  
  7. template <class TFunctor>
  8. class TIsCallable
  9. {   
  10.     typedef char TTwoChars[2];
  11.     template <class T>
  12.     static char Test(int[sizeof((*((T*)0))())]);
  13.  
  14.     template <class>
  15.     static TTwoChars& Test(...);
  16. public:
  17.     static const bool Value_ = sizeof(Test<TFunctor>(0)) == 1;
  18. };
  19.  
  20. int main()
  21. {   
  22.     std::cout
  23.         << TIsCallable<int>::Value_
  24.         << TIsCallable<P>::Value_
  25.         << TIsCallable<int (*)()>::Value_
  26.         << TIsCallable<S>::Value_ << std::endl;
  27. }
  28.  
Success #stdin #stdout 0.01s 2724KB
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https://ideone.com/W9q9H
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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