c++ - 警告 : "conversion from ' double' to 'int' , 可能丢失数据”

Question

我正在做以下 C++ 作业问题:

“编写一个程序，让用户将 12 个月中每个月的总降雨量输入 double 组。该程序应计算并显示当年的总降雨量、月平均降雨量以及降雨量最高的月份和最低金额。

输入验证:月降雨量数据不接受负数。”

我得到的错误是:

• 警告 2 警告 C4244:“=”:从“double”到“int”的转换，可能会丢失数据
• 警告 4 警告 C4244:“=”:从“double”到“int”的转换，可能会丢失数据
• 警告 1 警告 C4244:“初始化”:从“ double ”到“整数”的转换，可能丢失 数据
• 警告 3 warning C4244: 'initializing' : conversion from 'double' 到 'int'，可能丢失数据

阅读这些内容后，我想可以安全地假设我的代码中存在一些关于将 double 转换为整数的错误。我梳理了我的代码，寻找这些错误。我找到的那些int变量(根据Visual Studio 2012提供的行方向)，我改成了double；但它只会让我的代码更加困惑并产生更多错误。我什至出去把每个 int 变量都变成了一个 double 变量，结果却被关于“计数器”变量的 20 多个错误所困扰；错误说明“枚举类型”。

如有任何帮助，我们将不胜感激，该作业将于本周四下午(10 月 9 日)截止。

这个程序确实可以编译，但它也给了我各种垃圾答案和多余的垃圾答案。

到目前为止，这是我的代码:

#include<iostream>
#include<string>
using namespace std;

//Function prototypes
void totalAndAverage(int, double []);
void getHighest(int, double [], string []);
void getLowest(int, double [], string []);


//Global integer
const int SIZE = 12;
int main()
{
    //Create arrays
    double rainfallAmount[SIZE];
    int index;
    string months[SIZE] = { "January", "February", "March",
                         "April", "May", "June", 
                         "July", "August", "September", 
                         "October", "November", "December" };

    //Get the amount of rain for each month
    for ( index = 0; index < SIZE; index++)
    {
        cout << "Please enter the amount of rain (in inches) for month " << (index + 1) << ": " << endl; //+1 to not skip an array element
        cin >> rainfallAmount[index];

            //input validation, do not accept negative numbers
            while (rainfallAmount[index] < 0)
            {
                cout << "You cannot have a negative amount of rainfall. Please enter the amount of rain." << endl;
                cin >> rainfallAmount[index];
            }

    }

    //Call function to find total and average
    totalAndAverage(index, rainfallAmount);

    //Call function to find highest
    getHighest(index, rainfallAmount, months);

    //Call function o find lowest
    getLowest(index, rainfallAmount, months);

system("pause");
return 0;

}



void totalAndAverage(int i, double rainData[])
{
    double total = 0, average;

    //Find the total and average
    for (i = 0; i < SIZE; i++)
    {
        total += rainData[i];
    }
    //Display total
    cout << "The total rainfall is: " << total << endl;

    //Find average and display
    average = total / SIZE;
    cout << "The average monthly rainfall is: " << average << endl;
}



void getHighest(int iCount, double rainData2[], string monthData[])
{
    string highestMonth;

    //Initialize highest
    int highestRain = rainData2[0];

    //Find the highest
    for (iCount = 0; iCount < SIZE; iCount++)
    {
        if (rainData2[iCount] > highestRain)
        {
            highestRain = rainData2[iCount];
            highestMonth = monthData[iCount];

            //Display highest
            cout << highestMonth << " had the most rainfall this year with " << highestRain << " inches." << endl;
        }

    }
}



void getLowest(int counter, double rainData3[], string monthDataCopy[])
{
    string lowestMonth;

    //Initialize highest
    int lowestRain = rainData3[0];

    //Find the highest
    for (counter = 0; counter < SIZE; counter++)
    {
        if (rainData3[counter] > lowestRain)
        {
            lowestRain = rainData3[counter];
            lowestMonth = monthDataCopy[counter];

            //Display highest
            cout << lowestMonth << " had the least rainfall this year with " << lowestRain << " inches." << endl;
        }

    }
}

Answer 1

你写道:

 int highestRain = rainData2[0];
 int lowestRain = rainData3[0];

由于您希望在不四舍五入为整数的情况下找到最高值和最低值，因此您的“迄今为止最佳”变量需要是 double 值。您可以明确声明它们:

 double highestRain = rainData2[0];
 double lowestRain = rainData3[0];

您还可以使用 auto 关键字。 (参见 docs for Visual Studio 2012。)这种风格的优点和缺点超出了本答案的范围，但您可能应该了解语言功能。

 auto highestRain = rainData2[0];
 auto lowestRain = rainData3[0];