Question

这里是我当前代码的一部分（仍然不完整）。我试图将成本金额分配给* costPtr。但在分配之后，我在主函数中测试结果，看看我是否得到了我选择的正确值，结果似乎是0.00001而不是指定的值（299.9或349.99或999.99）。怎么了？我找不到答案。

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <ctype.h>

void DisplayApps(char *selectionPtr);
void SetCost(char selection, double *costPtr);
//void PaymentOptions(double *depositPtr, double cost);
//int Compare(double deposit, double choiceCost);
//void Pay(double *depositPtr, double choiceCost);
//void GetChanged(double *depositPtr, double choiceCost);
//void DoItAgain(char *quitPtr);

int main()
{
    char selection;
    char *selectionPtr;
    //double choiceCost;
    double *costPtr;
    //double *depositPtr;
    //char *quitPtr;

    printf("Welcome to the App Store\n");
    printf("***************************\n\n");
    DisplayApps(&selectionPtr);
    selection = selectionPtr;
    printf("Your choice %c\n", selection);
    SetCost(selection, &costPtr);
    printf("The cost of this item is %fl\n", costPtr);

    return 0;
}

void DisplayApps(char *selectionPtr)
{
    printf("-------------------------\n");
    printf("HERE ARE THE SLECTIONS\n");
    printf("C -- Clown Punching             $299.99\n");
    printf("V -- Virtual Snow Globe         $349.99\n");
    printf("R -- Remote PC                  $999.99\n");
    printf("G -- Grocery List Helper        $2.99\n");
    printf("M -- Mobile Cam Viewer          $89.99\n");
    printf("\n");

    printf("Please enter a selection: ", *selectionPtr);
    scanf(" %c", &*selectionPtr);

}

void SetCost(char selection, double *costPtr)
{
    double c = 299.99;
    double v = 349.99;
    double r = 999.99;
    double g = 2.99;
    double m = 89.99;
    if (selection == "C" || selection == "c")
    {
        *costPtr = c;
    }
    else if (selection == "V" || selection == "v")
    {
        *costPtr = v;
    }
    else if (selection == "R" || selection == "r")
    {
        *costPtr = r;
    }
    else if (selection == "G" || selection == "g")
    {
        *costPtr = g;
    }
    else if (selection == "M" || selection == "m")
    {
        *costPtr = m;
    }
}

Answer 1

您的程序格式错误且使用未定义的行为，因为您在SetCost参数上使用double**呼叫double*。

您最好在cost中将double变量声明为正常main：

int main()
{
    // ...
    double cost;
    // ...
    SetCost(selection, &cost);
    printf("The cost of this item is %fl\n", cost);
    // ...
}

Answer 2

在main中，声明double cost并将&cost传递给SetCost。然后打印cost。如果启用了警告，那么您的编译器可能会遇到问题。例如，当您正在寻找double **时，您已将SetCost传递给double *。

结果似乎是0.00001而不是我指定的值。为什么？

2 个答案: