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  1. #include <type_traits>
  2. #include <utility>
  3. #include <iostream>
  4.  
  5. template <typename T, typename = void>
  6. struct Comparator
  7. {
  8. 	int operator()(const T& a, const T& b) const
  9. 	{
  10. 	    std::cout << "catch all\n";
  11. 	    if (a < b)
  12. 	    {
  13.         	return -1;
  14.     	}
  15.     	if (a > b)
  16.     	{
  17.         	return 1;
  18.     	}
  19.     	return 0;
  20. 	}
  21. };
  22.  
  23. template <typename T>
  24. struct Comparator<T, std::enable_if_t<std::is_integral<T>::value && std::is_signed<T>::value>>
  25. {
  26. 	int operator()(const T &a, const T &b) const
  27. 	{
  28. 	    std::cout << "Signed arithmetic type\n";
  29. 	    return a - b;
  30. 	}
  31. };
  32.  
  33. template<typename T>
  34. int comparator(const T& a, const T& b)
  35. {
  36.     return Comparator<T>()(a, b);
  37. }
  38.  
  39. int main()
  40. {
  41.     comparator(42, 0);
  42.     comparator('c', 'g');
  43.     comparator(42u, 0u);
  44.     comparator(42LL, 0LL);
  45.     comparator(std::string("b"), std::string("a"));
  46. }
Success #stdin #stdout 0s 3468KB
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Standard input is empty
stdout
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Signed arithmetic type
Signed arithmetic type
catch all
Signed arithmetic type
catch all
https://ideone.com/8wm54h
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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