C计算器程序输出0

Question

尝试编写一个简单的程序，使用常量变量计算给定天数内的体重减轻量。一切看起来都对，但它输出 0 作为答案？任何帮助将非常感激!

#include <stdio.h>
#include <stdlib.h>

int main(){

double days; //declaring variables that will be enetred by user
const float weightLoss = 0.04; //declaring constant to be used in calculation
float overallLoss; //float that is used to display overall result

printf("Please enter how many days you are going to fast for: \n"); 
scanf("%f", &days); //scans keyboard for input and assigns to designated variable
printf("You entered: %f\n", days); 

overallLoss = days * weightLoss; 

printf("You will lose %.2f stone", overallLoss); //print of the final result

}

Answer 1

你有双天;，所以你需要scanf("%lf", &days)。或者您可以使用具有当前格式的 float days;。

使用printf()，您不需要l；使用 scanf()，这很重要。

不要忘记以换行符结束输出；你最后一个 printf() 少了一个。此外，某些编译器(例如 GCC 和 clang)将提供有关格式字符串和提供的类型之间的此类不匹配的警告。确保您使用适当的选项(例如 gcc -Wall)来诊断它们。

工作代码

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    double days;
    const float weightLoss = 0.04; // Dimension: stone per day
    float overallLoss;

    printf("Please enter how many days you are going to fast for: ");
    if (scanf("%lf", &days) != 1)
    {
        fprintf(stderr, "Oops!\n");
        exit(1);
    }
    printf("You entered: %13.6f\n", days);

    overallLoss = days * weightLoss;

    printf("You will lose %.2f stone\n", overallLoss);

    return 0;
}

示例输出

第一次运行:

Please enter how many days you are going to fast for: 12
You entered:     12.000000
You will lose 0.48 stone

第二次运行:

Please enter how many days you are going to fast for: a fortnight
Oops!

如果您还没有了解这些，只要您准确输入，就可以放弃 if 测试；它必须是一个可识别的数字。

替代代码

使用 float days 而不是 double days。

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
    float days;
    const float weightLoss = 0.04; // Dimension: stone per day
    float overallLoss;

    printf("Please enter how many days you are going to fast for: ");
    if (scanf("%f", &days) != 1)
    {
        fprintf(stderr, "Oops!\n");
        exit(1);
    }
    printf("You entered: %13.6f\n", days);

    overallLoss = days * weightLoss;

    printf("You will lose %.2f stone\n", overallLoss);

    return 0;
}

示例输出

Please enter how many days you are going to fast for: 10
You entered:     10.000000
You will lose 0.40 stone