C++ C++；将输入字符串与字符串进行比较会警告我从double转换为int-可能会丢失数据

我必须编写一个程序，要求用户提供重量和行星名称。程序必须输出用户在那个星球上的体重。由于某些原因，我得到错误：“'=”：从“double”转换为“int”，可能会丢失数据

在我尝试使用（行星=水星）之前，但仍然没有运气

这是我的密码：

    // ConsoleApplication5.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
#include <string>
#include <sstream>
#include "ConsoleApplication5.h"

using namespace std;

int main()
{
    cout << "Assignment 05" << endl;


    int weight = 0;
    string planet = "";
    int weightOnplanet;
    string entry = "You entered a weight of ";

    string Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto;

    cout << "Please Enter Weight <as an integer of pounds>: " << endl;
    cin >> weight;
    cout << "Please Enter Planet name <ie: Earth>: " << endl;
    cin >> planet;
    cout << entry << weight << " and a planet name of " + planet << endl;



    if (planet == Mercury)
    {
        weightOnplanet = weight * 0.4155;
        cout << "On a " + planet + " your weight in pounds would be " << weightOnplanet << endl;
    }
    else if (planet == Venus)
    {
        weightOnplanet = weight * 0.8975;
        cout << "On a " + planet + " your weight in pounds would be " << weightOnplanet << endl;
    }
    else if (planet == Earth)
    {
        weightOnplanet = weight * 1.0;
        cout << "On a " + planet + " your weight in pounds would be " << weightOnplanet << endl;
    }
    else if (planet == Mars)
    {
        weightOnplanet = weight * 0.3507;
        cout << "On a " + planet + " your weight in pounds would be " << weightOnplanet << endl;
    }
    else if (planet == Jupiter)
    {
        weightOnplanet = weight * 2.5374;
        cout << "On a " + planet + " your weight in pounds would be " << weightOnplanet << endl;
    }
    else if (planet == Saturn)
    {
        weightOnplanet = weight * 1.0677;
        cout << "On a " + planet + " your weight in pounds would be " << weightOnplanet << endl;
    }
    else if (planet == Uranus)
    {
        weightOnplanet = weight * 0.8947;
        cout << "On a " + planet + " your weight in pounds would be " << weightOnplanet << endl;
    }
    else if (planet == Neptune)
    {
        weightOnplanet = weight * 1.1794;
        cout << "On a " + planet + " your weight in pounds would be " << weightOnplanet << endl;
    }
    else if (planet == Pluto)
    {
        weightOnplanet = weight * 0.0899;
        cout << "On a " + planet + " your weight in pounds would be " << weightOnplanet << endl;
    }
    else
        cout << "Unknown Planet" << endl;

    system("pause");
    return 0;
}

//ConsoleApplication5.cpp：定义控制台应用程序的入口点。
//
#包括“stdafx.h”
#包括
#包括
#包括
#包括“控制台应用程序5.h”
使用名称空间std；
int main（）
{
库特星球；
cout每个行星变量（水星、金星等）都应该有一个实际值，例如：

Mercury = "Mercury";

字符串不是用变量名初始化的，你必须给它一个值

你甚至不必为每颗行星都设定一个变量。你可以这样做：

if(planet == "Mercury")

每个行星变量（水星、金星等）应具有实际值，例如：

Mercury = "Mercury";

字符串不是用变量名初始化的，你必须给它一个值

你甚至不必为每颗行星都设定一个变量。你可以这样做：

if(planet == "Mercury")

你得到的警告是为了

weightOnplanet = weight * 0.4155;

由于
weightOnPlanet
是
int
并且
weight*0.4155
是双倍，您将失去精度。您可能希望
weightOnPlanet
是
double
而不是
int

只需提及
如果（planet==Mercury）
会将
planet
与空字符串进行比较，这就是为什么您会得到不想要的结果，直到您执行@ErrorAtLine0提到的操作。
您收到的警告是针对

weightOnplanet = weight * 0.4155;

由于
weightOnPlanet
是
int
并且
weight*0.4155
是双倍，您将失去精度。您可能希望
weightOnPlanet
是
double
而不是
int

<> >只需提到<代码>（行星=水星）<代码>将比较<代码>行星<代码>空字符串，这就是为什么你会得到不希望的结果，直到你做了@ ErrRotry0所提到的。
谢谢，那个固定的“警告”警报。谢谢解释，我很感激-因为我刚开始学习C++。谢谢，那是固定的。警告“谢谢”，谢谢你的解释，我很感激，因为我刚开始学习C++。