Question

我正在为一个必须使用函数的类编写一个程序，我没有得到任何语法错误，并且多次尝试改变事情没有成功。该功能未正确保存到.out文件中。

以下是代码：

/* LAB13, functions                                       */
/* Given the number of sides of an n-side regular polygon */
/* and the radius of the circle, find the perimeter and   */
/* area of the polygon                                    */

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define IN_FILE "lab13.dat"
#define OUT_FILE "lab13.out"

/* function prototypes */
double get_perimeter(double n, double radius);
double get_area(double n, double radius);

int main(void)
{
        double n;               /* number of sides          */
        double radius;          /* radius of the circle     */
        double area;            /* area of the polygon      */
        double perimeter;       /* perimeter of the polygon */

    FILE * data_in;     /* input file pointer  */
    FILE * data_out;    /* output file pointer */

    /* Open the two required files */
    data_in = fopen(IN_FILE, "r");
    if (data_in == NULL)
    {
        printf("Error on fopen file %s \n", IN_FILE);
        exit(EXIT_FAILURE);
    }

    data_out = fopen(OUT_FILE, "w");
    if (data_out == NULL)
    {
        printf("Error on fopen file %s \n", OUT_FILE);
        exit(EXIT_FAILURE);
    }
    /* Print headers */
    fprintf(data_out, "\nScott _________. Lab13. \n\n");
    fprintf(data_out, " Number Of Sides     Radius    Perimeter      Area    \n");
    fprintf(data_out, "   of Polygon      of Circle   of Polygon   of Circle \n");
    fprintf(data_out, "----------------   ---------   ----------   --------- \n");
    while ((fscanf(data_in, "%lf%lf", &n, &radius))== 2)
        {
           perimeter = get_perimeter(n, radius);
           area      = get_area(n, radius);
           fprintf(data_out,"%8i  %17.3f  %11.3f  %10.3f\n",
               n, radius, perimeter, area);
        }
    printf("\n");
    fclose(data_in);
    fclose(data_out);
    return EXIT_SUCCESS;
}

/*-----------------------------------------------------------*/
double get_perimeter(double n, double radius)
{
  double perimeter;

  perimeter = 2 * n * radius * (sin(M_PI/n));
  return perimeter;
}

/*-----------------------------------------------------------*/
double get_area(double n, double radius)
{
  double area;

  area = 0.5 * n * (radius*radius) * (sin(2*M_PI)/n);
  return area;
}

/*-----------------------------------------------------------*/

它正在抓取的lab13.dat文件是：

3.0 16.5
5.0 9.1
7.0 11.5
The output from running the program

Answer 1

您正在使用n格式打印double %8i，该格式需要int。如果要打印double但禁止任何可能的非整数部分，请使用精度0，如%8.0f中所示。

Answer 2

你的问题在于fprintf。

fprintf(data_out,"%8i  %17.3f  %11.3f  %10.3f\n", n, radius, perimeter, area);

我不是你想要的格式说明符，使用f。可能是一个错字

C函数不返回

2 个答案: