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  1. #include <cstddef>
  2. #include <iostream>
  3.  
  4. template <typename T> struct Printable
  5. {
  6.     Printable(const T& val) : val(val) {}
  7.     void print(std::ostream& out) const {out << val;}
  8.     const T& val;
  9. };
  10.  
  11. template <> struct Printable<std::nullptr_t>
  12. {
  13.     Printable(nullptr_t) {}
  14.     void print(std::ostream& out) const {out << "null";}
  15. };
  16.  
  17. template <typename T>
  18. Printable<T> printable(const T& value) {return Printable<T>(value);}
  19.  
  20. template <typename T>
  21. std::ostream& operator<<(std::ostream& out, const Printable<T>& p)
  22. {
  23.     p.print(out);
  24.     return out;
  25. }
  26.  
  27. int main()
  28. {
  29. 	std::cout << printable(42) << " " << printable(nullptr) << "\n";
  30. 	return 0;
  31. }
Success #stdin #stdout 0s 3340KB
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stdin
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Standard input is empty
stdout
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42 null
https://ideone.com/9dcoL9
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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