定义一个函数式宏diff（x, y）,返回x， y的差。

1、

#include <stdio.h>

#define diff(x, y) ((x) - (y))

int main(void)
{
    int a, b;
    puts("please input two integers.");
    printf("a = "); scanf("%d", &a);
    printf("b = "); scanf("%d", &b);
    printf("the diff of a and b is: %d\n\n\n", diff(a, b));
    
    double c, d;
    puts("please input two real numbers.");
    printf("c = "); scanf("%lf", &c);
    printf("d = "); scanf("%lf", &d);
    printf("the diff of c and d is: %f\n", diff(c, d));
    
    return 0;
}