我将如何设置函数来计算圆的面积 - C

Question

我有这个 C 程序需要计算用户输入的圆的面积。我必须在主要功能之前使用它：

void area_circum(double radius, double *area, double *circum);

我无法让程序运行。我正在使用主要功能和另一个名为 area_circum();

这是我现在拥有的：

#include <stdio.h>


void area_circum(double radius, double *area, double *circum);

int main(void) {

    double radius, area, circum;

    printf("Please enter the radius of the circle: ");
    scanf("%f", &radius);

    area_circum(radius, area, circum);

    printf("Area of circle : %0.4f\n", area);

    return 0;
}


void area_circum(double radius, double *area, double *circum) {
    double PIE = 3.141;

    double areaC = 0;

    areaC = PIE * radius * radius;
}

当我构建它并运行它时，它起作用了，我输入了一个数字，但随后它 returns 0.00

Answer 1

#include <stdio.h>

void area_circum(double radius);

int main() {

   double radius;

   printf("Please enter the radius of the circle: ");

   scanf("%lf", &radius);

   area_circum(radius);

   return 0;

}


void area_circum(double radius) {

   double PIE = 3.141;

   double areaC = 0;

   areaC = PIE * radius * radius;

   printf("Area of circle : %0.4f\n", areaC);

}

Answer 2

你快到了。您需要做的就是 return 计算出的值：

void area_circum(double radius, double *area) {
    double PIE = 3.141;
    *area = PIE * radius * radius;
}

并像这样打电话：

    area_circum(radius, &area);

Answer 3

从函数的名称和签名可以看出，它应该同时计算面积和周长。同样很明显，您应该将两个 int 变量（或两个指向 int 的指针）的地址传递给它，然后将给出计算结果：

#include <stdio.h>

void area_circum(double radius, double *area, double *circum);

int main(void)
{
    double radius, area, circum;

    printf("Please enter the radius of the circle: ");
    scanf("%lf", &radius); // Note: You should add a check to see if
                           //       scanf() failed.
    area_circum(radius, &area, &circum);  // &area is the address of area
                                          // &circum is the address of circum
    printf("Area of circle : %0.4f\n", area);
    printf("Circumference of circle : %0.4f\n", circum);
    return 0;
}

void area_circum(double radius, double *area, double *circum)
{
    double PIE = 3.1416;
    *area = PIE * radius * radius;
    *circum = PIE * radius * 2;
}

我将如何设置函数来计算圆的面积 - C

How would I set up function to calculate the area of a circle - C

c

function

area