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  1. #include <iostream>
  2. #include <type_traits>
  3.  
  4. template <typename T>
  5. struct A {
  6.     int val = 0;
  7.  
  8.     template<typename Integer
  9.             ,typename  = typename std::enable_if<T::value && sizeof(Integer)>::type
  10.             >
  11.     A(Integer n) : val(n) {};
  12.  
  13.     A(...) {}
  14.     /* ... */
  15. };
  16.  
  17. struct YES { constexpr static bool value = true; };
  18. struct NO { constexpr static bool value = false; };
  19.  
  20. int main() {
  21.     A<YES> y(10);
  22.     A<NO> n;
  23.     std::cout << "YES: " << y.val << std::endl
  24.               << "NO:  " << n.val << std::endl;
  25. }
Success #stdin #stdout 0s 2896KB
comments (?)
stdin 
Standard input is empty
stdout 
YES: 10
NO:  0
https://ideone.com/2Gnyzj
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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