C语言在#define中带参数出错，为什么

Question

#include
#define FUNC(X,Y) (1/(X)+1/(Y))
int main(void)
{
double x=FUNC(2,2);
printf("%lf\n",x);
return 0;
}
在VS2013中编译没有错误，但是输出结果是0.000000，为什么？是#define用错了吗？

Answer 1

In C the divide between int also return int

so 1/2=0
so 1/2 + 1/2 = 0

solution
#define func(x,y) (1.0/(x)+1.0/(y))