C计算器程序输出0

Question

尝试制作一个简单的程序，使用常量变量计算给定天数内的重量损失量。一切看起来都对我而且输出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

您有double days;，因此您需要scanf("%lf", &days)。或者您可以使用当前格式的float days;。

使用printf()，您不需要l;与scanf()一起，这是至关重要的。

不要忘记用换行符结束输出;你的上一个printf()遗失了一个。此外，一些编译器（例如GCC和clang）将提供有关格式字符串与提供的类型之间不匹配的警告。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

首先运行：

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

第二轮：

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

只要您准确输入输入，如果您还没有了解这些测试，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代替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