代码示例：

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/* subst.c -- 在字符串中进行替换 */
#include <stdio.h>
#define PSOR(x) printf("The square of " #x " is %d\n", ((x)*(x)))

int main(void){
	int y = 5;
	PSOR(y);
	PSOR(2 + 4);
	return 0;
}

运行结果为：

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The square of y is 25
The square of 2 + 4 is 36