为什么程序提供 -143155...当我只从 int 切换到 double？

Question

如果我使用 float 或 double 而不是 int，为什么这段代码会给出完全错误的答案？

//C How to Program Exercises 2.33
#include <stdio.h>
#include <conio.h>
double dailyDrivingCost(double miles, double costPerGallon,double averageMilesPerGallon);
int main(void){
    double a,b,c,d,e;
    printf ("Please enter the number of miles daily\n");
    scanf("%lf",&a);
    printf ("Please enter the cost per gallon\n");
    scanf("%lf",&b);
    printf ("Please enter the average miles per gallon\n");
    scanf("%lf",&c);
    printf ("The number of miles per gallon is:%d",dailyDrivingCost(a,b,c));
getch();
return 0;
}
double dailyDrivingCost(double miles, double costPerGallon,double averageMilesPerGallon){
      double overall_cost;
      overall_cost= (miles/averageMilesPerGallon)+ costPerGallon;

      return overall_cost;
}

Answer 1

改变

printf ("The number of miles per gallon is:%d",dailyDrivingCost(a,b,c));
                                            ^

到

printf ("The number of miles per gallon is:%f",dailyDrivingCost(a,b,c));

d转换说明符用于打印int，打印double（或float）需要f转换说明符.

为什么程序提供 -143155...当我只从 int 切换到 double？

Why does program provide -143155...when I only switched from int to double?

c

double

int