subst.c

C Primer Plus(第五版)中文版,不用多说了

/* subst.c -- substitute in string */
#include <stdio.h>
#define PSQR(x) printf("The square of " #x " is %d.\n",((x)*(x)))

int main(void)
{
    int y = 5;

    PSQR(y);
    PSQR(2 + 4);
    
    return 0;
}