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  1. #include <iostream>
  2. #include <sstream>
  3. #include <cstdint>
  4.  
  5. struct Callback
  6. {
  7. 	virtual void dosomething(uint8_t level, const char *msg) = 0;
  8. };
  9.  
  10. Callback *callback = nullptr;
  11.  
  12. void log_impl(std::ostream&) {}
  13.  
  14. template<typename T, typename ... Args>
  15. void log_impl(std::ostream &os, const T &first_arg, const Args&... args)
  16. {
  17.     os << first_arg;
  18.     log_impl(os, args...);
  19. }
  20.  
  21. template<typename ... Args>
  22. void log(uint8_t level, const Args&... args)
  23. {
  24.     std::ostringstream msg;
  25.     log_impl(msg, args...);
  26.     callback->dosomething(level, msg.str().c_str()); // some api
  27. }
  28.  
  29. struct MyCallback : Callback
  30. {
  31. 	void dosomething(uint8_t level, const char *msg) override { std::cout << "[" << int(level) << "]: " << msg << std::endl; }
  32. };
  33.  
  34. int main()
  35. {
  36. 	MyCallback cb;
  37. 	callback = &cb;
  38.  
  39. 	log(1, "Hello ", "World", '!', " ", 12345);
  40.  
  41. 	return 0;
  42. }
Success #stdin #stdout 0.01s 5444KB
comments (?)
stdin
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Standard input is empty
stdout
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[1]: Hello World! 12345
https://ideone.com/y8Rksb
language:
C++ 4.3.2 (gcc-4.3.2)
created:
5 years ago
visibility:
public

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