Question

晚上好。我刚开始在大学里学习C，我们的第一个任务就是制作一个计算用户bmi的程序。对于我的生活，我无法弄清楚为什么我没有得到我想要的结果。无论身高和高度重量我提交给程序...我继续得到像4258544这样可笑的高bmi然后它告诉我我体重不足。我以为我可以用另一双眼睛。请帮忙。

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

void h_conversion (double *h) {
    *h = *h/12;
}

int bmi_category (double h, double w, double b) {
    b = (w * 4.88)/(h * h);
    if (b < 20)
        return 1;
    else if (b >= 20 && b < 25)
        return 2;
    else if (b >= 25 && b < 30)
        return 3;
    else if (b >= 30 && b < 40)
        return 4;
    else
        return 5;
}

int main (void) {

    double height, weight, bmi;
    double *h, *w, *b;
    h = &height;
    w = &weight;
    b = &bmi;

    printf ("Please enter height (inches): \n");
    scanf (" %lf", &height);

    while ( h <= 0 ) {
        printf ("Weee, this is fun! Try again.\n");
        scanf (" %.2lf", &height);
    }

    if ( *h < 42 || *h > 84 ) 
        printf ("Your entry falls outside the norm for an adult.\n");

    h_conversion( h );

    printf ("Please enter weight (lbs): \n");
    scanf (" %.2lf", &weight);

    while ( w <= 0 ) {
        printf ("This is why we can't have nice things.  Try again.\n");
        scanf (" %.2lf", &weight);
    }

    switch ( bmi_category(*h, *w, *b)) {

    case 1:
        printf ("BMI: %d. Underweight.", (int)&bmi);
        break;
    case 2:
        printf ("BMI: %d. Normal weight.", (int)&bmi);
        break;
    case 3:
        printf ("BMI: %d. Slightly overweight.", (int)&bmi);
        break;
    case 4:
        printf ("BMI: %d. Overweight.", (int)&bmi);
        break;
    case 5:
        printf ("BMI: %d. Extremely overweight.", (int)&bmi);
        break;
    default:
        printf ("error condition\n");
    }
    system ("pause");
    return 1;
}

Answer 1

在您的打印中，您正在使用

(int)&bmi
// this request the address of bmi and casts that value to an integer (addresses are always integers)

何时使用

(int)bmi
// this casts the value of the variable bmi to an integer which is what you want.

您总是得到的奇怪价值是因为您获取地址而不是变量值。

还有为什么所有指针变量？你只需要一个。 bmi函数不要求你使用指针，那么为什么要使用它们而不是它的非指针对应物？

当主要执行完毕且没有任何问题时，主要返回0。由于某种原因，您返回1表示该程序没有正确完成执行。

Answer 2

在您对bmi_category功能的调用中，参数传递不正确。您在预期指针时传递了值。因此，计算出的bmi的值是bmi_category函数的本地值，不会更新给调用者。

打印bmi的值时，您打印的是地址&bmi，而不是值。

这是固定代码，稍加清理：

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

void h_conversion(double *h) {
    *h = *h / 12;
}

int bmi_category(const double *h, const double *w, double *b) {
    *b = (*w * 4.88) / (*h * *h);
    if (*b < 20)
        return 1;
    else if (*b >= 20 && *b < 25)
        return 2;
    else if (*b >= 25 && *b < 30)
        return 3;
    else if (*b >= 30 && *b < 40)
        return 4;
    else
        return 5;
}

int main(void) {

    double height, weight, bmi;

    printf("Please enter height (inches): \n");
    scanf(" %lf", &height);

    while (height <= 0) {
        printf("Weee, this is fun! Try again.\n");
        scanf(" %lf", &height);
    }

    if (height < 42 || height > 84)
        printf("Your entry falls outside the norm for an adult.\n");

    h_conversion(&height);

    printf("Please enter weight (lbs): \n");
    scanf(" %lf", &weight);

    while (weight <= 0) {
        printf("This is why we can't have nice things.  Try again.\n");
        scanf(" %lf", &weight);
    }

    switch (bmi_category(&height, &weight, &bmi)) {

    case 1:
        printf("BMI: %d. Underweight.", (int)bmi);
        break;
    case 2:
        printf("BMI: %d. Normal weight.", (int)bmi);
        break;
    case 3:
        printf("BMI: %d. Slightly overweight.", (int)bmi);
        break;
    case 4:
        printf("BMI: %d. Overweight.", (int)bmi);
        break;
    case 5:
        printf("BMI: %d. Extremely overweight.", (int)bmi);
        break;
    default:
        printf("error condition\n");
    }
    system("pause");
    return 1;
}

有人可以为什么这个程序运行不正常。我是C的新手

2 个答案: