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  1. #include <iostream>
  2. #include <cstring>
  3. #include <cmath>
  4. using namespace std;
  5.  
  6. #define PRINT1(...) printf(__VA_ARGS__)
  7. #define PRINT2(X, ...) printf("Message "#X": ", ##__VA_ARGS__)
  8.  
  9. #define PRINT3(...) printf(##__VA_ARGS__)
  10. #define PRINT4(X, ...) printf("Message "#X": " ##__VA_ARGS__)
  11.  
  12. int main()
  13. {
  14. //__VA_ARGS__
  15. 	double a = 40;
  16.     double b = sqrt(a);
  17. 	PRINT1("Hello~ \n");							//Hello~
  18. 	PRINT1("a = %f, b = %.3f \n", a, b);			//a = 40.000000, b = 6.325
  19. 	PRINT2(0);										//Message 0: 
  20.     PRINT2(1, "a = %.2f, b = %.4f\n", a, b);		//why??? Expect: Message 1: a = 40.00, b = 6.3246; Result: Message 1:  
  21. 	printf("\n\n\n");
  22.  
  23. //##__VA_ARGS__
  24. 	//PRINT3("Hello~ \n");							//Compile error, why???
  25. 	//PRINT3("a = %f, b = %.3f \n", a, b);			//Compile error, why???
  26. 	PRINT4(0);										//Message 0: 
  27.     //PRINT4(1, "a = %.2f, b = %.4f\n", a, b);		//Compile error, why???
  28.  
  29. 	return 0;
  30.  
  31. }
Success #stdin #stdout 0.01s 5272KB
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stdin
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Standard input is empty
stdout
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Hello~ 
a = 40.000000, b = 6.325 
Message 0: Message 1: 


Message 0:
https://ideone.com/cS0XH4
language:
C++ (gcc 8.3)
created:
139 days ago
visibility:
secret

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