Question

我的简单旅行计划的代码如下，我一直在圈子里四处走动。我可以把它归结为一个错误，它说：

（变量'fuel'正在使用而未初始化）......

我陷入困境，寻找暗示/提示或帮助下一步做什么。如果您对此有任何疑问，请询问，如果有任何提示使其成为更好的帖子，请告诉我。

由于

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

void WelcomeMessage();
void AskUserForInput();
void PrintTripSummary(float avgMiles, float minCost, float maxCost, float travelMiles, float fuel);

int main()
{
    WelcomeMessage();
    AskUserForInput();
    printf("\nThank you, please drive safely and have a nice trip!\n");
    return 0;
}

void WelcomeMessage()
{
    printf("Welcome to the Trip Planner!");
    printf("So you are ready to take a trip? Let me help you plan for\n");
    printf("your fuels costs and required stops to fill up your tank.\n");
    printf("============================================================\n");
    printf("Please provide answers to the prompts below and I will\n");
    printf("display a summary for you when I have computed the results.\n");
    printf("============================================================\n");
}

void AskUserForInput()
{
    float avgMiles, minCost, maxCost, travelMiles, fuel;
    do {
        printf("Input your car's average miles per gallon (enter 0 to quit) ");
        scanf("%f", &avgMiles);
        if (avgMiles == 0)
            break;
        printf("The lowest estimated price per gallon of fuel is: ");
        scanf("%f", &minCost);
        printf("The highest estimated price per gallon of fuel is: ");
        scanf("%f", &maxCost);
        printf("How many miles you plan to travel: ");
        scanf("%f", &travelMiles);
        PrintTripSummary(avgMiles, minCost, maxCost, travelMiles, fuel);
    } while (avgMiles != 0);
}

void PrintTripSummary(float avgMiles, float minCost, float maxCost, float travelMiles, float fuel)
{
    fuel = avgMiles/travelMiles;
    minCost = fuel*minCost;
    maxCost=fuel*maxCost;
    printf("== == == == == == == = Trip Summary == == == == == == == == == == \n\n");
    printf("You will need to purchase %.2f gallons of fuel.\n");
    printf("The approximate cost of fuel for your trip is between $%5.2f and $%5.2f \n",&minCost,&maxCost);
    printf("Thank you, please drive safely and have a nice trip!\n\n");
    printf("== == == == == == == = End Trip Summary == == == == == == == == ==\n\n");
}

Answer 1

您没有在fuel中为局部变量AskUserForInput()提供值。

Answer 2

什么是导致错误而不是警告的编译器设置，BTW？但是，是的，你正在使用未经初始化的燃料 -

PrintTripSummary(avgMiles, minCost, maxCost, travelMiles, fuel);

我发现基本上这并不重要，因为实际上该功能不使用燃料。但编译器没有看到它，可能不是在它下面声明它时，如果它在另一个编译单元中它绝对不能。因此，要么从参数列表中取出燃料，要么在拨打电话之前添加

fuel = 0.0f;

此外，请注意您代替：

void WelcomeMessage();

你真的想要：

void WelcomeMessage(void);

由于向后兼容的原因，C中的第一个没有声明参数的类型，并且无论放入什么内容都不会发出警告。

Answer 3

一些事情：

AskUserForInput()没有读取燃油值，因此当它传递给PrintTripSummary()
您在fuel中可能不需要PrintTripSummary()参数，而是在那里进行计算。只需删除参数，将燃料声明为局部变量并在那里计算
您没有在fuel

printf("You will need to purchase %.2f gallons of fuel.\n");

无效的陈述麻烦

3 个答案: