你能帮我一个简短code，可以打印自己？ [英] Can you help me with a short code that can print itself?

问题描述

#define q(k)main(){return!puts(#k"\nq("#k")");}
q(#define q(k)main(){return!puts(#k"\nq("#k")");})

这code可以在屏幕上打印本身，但是，我有困难阅读它，尤其是两个＃K，它是如何工作的？我知道问：如何＃定义（K）2 * K的作品，但我真的没有这code.请主意帮我分析吧！谢谢！

This code can print itself on the screen,however,I have a difficulty in reading it,especially that two #K,how does it work?I know how #define q(k) 2*k works,but I really have no idea about this code.Please help me to analyse it!thank you!

推荐答案

简化呼叫，并用你的编译器的preprocessor，看看是怎么回事：

Simplify the call and use your compiler's preprocessor to see what is going on:

#define q(k)main(){puts(#k"hello("#k")");}
q(argument)

运行的gcc -E 上，让你：

main(){puts("argument""hello(""argument"")");}

正如你所看到的，什么情况是，该参数的①宏被改造成一个字符串（因为被用作 #K - 这有时被称为字符串化）。有没有其他的魔法会在这里。

As you can see, what happens is that the argument to the q macro gets transformed into a string (because is is used as #k - this is sometimes called "stringification"). There is no other magic going on here.

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