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  1. #include <iostream>
  2. #include <type_traits>
  3.  
  4. using namespace std;
  5.  
  6. // Variant 1:
  7.  
  8. class I1 {
  9. public:
  10.     virtual ~I1() {}
  11. };
  12.  
  13. // Variant 2.1:
  14.  
  15. class I21 {
  16. public:
  17.     virtual ~I21() = 0;
  18. };
  19.  
  20. I21::~I21() {}
  21.  
  22. // Variant 2.2:
  23.  
  24. class I22 {
  25. public:
  26.     virtual ~I22() = 0;
  27. };
  28.  
  29. I22::~I22() = default;
  30.  
  31. int main() {
  32. 	cout << boolalpha << "std::is_abstract:\n"; 
  33.  
  34. 	cout << "I1:  " << std::is_abstract<I1>::value << '\n';
  35. 	cout << "I21: " << std::is_abstract<I21>::value << '\n';
  36. 	cout << "I22: " << std::is_abstract<I22>::value << '\n';
  37.  
  38. 	return 0;
  39. }
Success #stdin #stdout 0s 3412KB
comments (?)
stdin 
Standard input is empty
stdout 
std::is_abstract:
I1:  false
I21: true
I22: true
https://ideone.com/HL7OKe
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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