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  1. #include <iostream>
  2. using namespace std;
  3.  
  4.  
  5. template <typename T>
  6. struct check_valid_type {
  7.         typedef void type;
  8. };
  9.  
  10. struct foo;
  11.  
  12. template <typename T, typename I=void>
  13. struct bar {
  14. 	std::string get_int() {
  15. 		std::cout << "Invoking 1" << std::endl;
  16. 		return "--";
  17. 	}
  18. };
  19.  
  20. template <typename T>
  21. struct bar<T, typename check_valid_type<decltype(T::x)>::type> {
  22. 	std::string get_int() {
  23. 		std::cout << "Invoking 2" << std::endl;
  24. 		return T::x;
  25. 	}
  26. };
  27.  
  28.  
  29.  
  30. int main() {
  31. 	// your code goes here
  32. 	bar<foo> y;
  33. 	std::cout << y.get_int() << std::endl;
  34. 	return 0;
  35. }
  36.  
  37. struct foo {
  38. 	static constexpr const char* x = "hello";	
  39. };
  40.  
  41.  
Success #stdin #stdout 0.01s 5292KB
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stdin
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Standard input is empty
stdout
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Invoking 1
--
https://ideone.com/hQwS2b
language:
C++14 (gcc 8.3)
created:
17 hours ago
visibility:
public

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