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

Question

我必须编写一个程序，要求用户输入重量和行星名称。程序必须输出用户在那个星球上的体重。出于某种原因，我得到错误:“'=':从'double'到'int'的转换，可能会丢失数据。

在我尝试使用 (planet == Mercury) 但仍然没有运气之前。

这是我的代码:

    // 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;
}

Answer 1

每个行星变量(水星、金星等)都应该有一个实际值，例如:

Mercury = "Mercury";

字符串不会用变量名初始化，你必须实际给它一个值。

您甚至不必为每个行星都设置一个变量。你可以这样做:

if(planet == "Mercury")