如何在 C++ 中实现无操作宏(或模板)?

2021-12-13 00:00:00 c macros templates c++

如何在 C++ 中实现 no-op 宏?

How do I implement no-op macro in C++?

#include <iostream>   

#ifdef NOOP       
    #define conditional_noop(x) what goes here?   
#else       
    #define conditional_noop(x) std::cout << (x)   
#endif   
int main() {       
    conditional_noop(123);   
}

我希望在定义 NOOP 时不执行任何操作，并在未定义 NOOP 时打印123".

I want this to do nothing when NOOP is defined and print "123", when NOOP is not defined.

推荐答案

如前所述 - 没有.
此外，您的代码中存在印刷错误.
它应该是 #else 而不是 #elif.如果是#elif，则后面跟着新的条件

As mentioned before - nothing.
Also, there is a misprint in your code.
it should be #else not #elif. if it is #elif it is to be followed by the new condition

#include <iostream>   

#ifdef NOOP       
    #define conditional_noop(x) do {} while(0)
#else       
    #define conditional_noop(x) std::cout << (x)   
#endif

玩得开心编码！按照另一个答案中的建议添加了 [do] 结构以提高稳健性.

Have fun coding! added the [do] construct for robustness as suggested in another answer.

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