#define in C:发生了什么 [英] #define in C: what is happening

问题描述

有人可以解释每一步发生了什么吗?我知道最终输出是 140.5，但我不确定为什么会这样.导致 140.5 的每一行发生了什么?

Can someone explain what is happening at every step? I know the final output is 140.5, but I am unsure why that is. What is happening at each line that is resulting in 140.5?

#define PI 3.1
#define calcCircleArea(r) (PI * (r) * (r))
#define calcCylinderArea(r,h) (calcCircleArea(r) * h)
int main() {
    double i = calcCylinderArea(3.0,5.0 + 1); printf("%g", i);
}

推荐答案

Step 0

calcCylinderArea(3.0,5.0+1)

步骤 1

(calcCircleArea(3.0)*5.0+1)

注意不是(5.0+1).
问题从这里开始.

notice that it is not (5.0+1).
Problem begins here.

((PI*(3.0)*(3.0))*5.0+1)

步骤 3

((3.1*(3.0)*(3.0))*5.0+1)

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