fscanf 没有读取随机值，对吗？

Question

我试图从一个文件中读取一些数字并将 output 的结果读入另一个文件。 每次我尝试这样做时，即使对于我没有修改的值，我也会得到随机值。 我知道这可能与我阅读信息的方式有关，但我不确定。 lab4sample.dat 的内容

12.4   24.0
 5.6    8.0
7.85   12.0

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
//#define FILE_IN “lab4.dat”
#define FILE_IN "lab4sample.dat"

double areaPolygon(double radius, double nsides);
double perimeterPolygon(double radius, double nsides);

int main(void)
{
     FILE * infile;
     FILE * answer_file;

     double radius;
     double nsides;
     double area;
     double perimeter;

     infile = fopen(FILE_IN,"r");
     if(infile == NULL)
     {
         printf("Error on opening the data file\n");
         exit(EXIT_FAILURE);
     }

     answer_file = fopen("lab4.out","w");
     if(answer_file == NULL)
     {
         printf("Error on opening the output file\n");
         exit(EXIT_FAILURE);
     }

     fprintf(answer_file, "\n  Lab 4.\n\n");
     fprintf(answer_file, "            Number      Perimeter      Area Of  \n");
     fprintf(answer_file, " Radius    Of Sides    Of Polygon      Polygon  \n");
     fprintf(answer_file, "--------   --------   ------------   ----------- \n");

     while((fscanf(infile, "%lf %lf\n",&radius, &nsides))== 2)
     {
         area = areaPolygon(radius,nsides);
         perimeter = perimeterPolygon(radius,nsides);
         fprintf(answer_file,"%5.2f %5.2f %5.2f %5.2f \n",&radius,&nsides,&area,&perimeter);
     }

 }

Answer 1

     fprintf(answer_file,"%5.2f %5.2f %5.2f %5.2f \n",&radius,&nsides,&area,&perimeter);

您正在打印radius 、 nsides 、 area和perimeter的地址。 &运算符获取变量的地址。 你想打印它们的值。

Answer 2

您正在尝试将指针打印为浮点数（您的编译器应该抱怨）。 改变：

fprintf(answer_file,"%5.2f %5.2f %5.2f %5.2f \n",&radius,&nsides,&area,&perimeter);

至：

fprintf(answer_file,"%5.2f %5.2f %5.2f %5.2f \n", radius, nsides, area, perimeter);