我正在编写作业程序，到目前为止，除了“海王星”行星以外，其他所有东西都可以正确打印。其他所有选择都可以正常工作并按预期方式打印出数字，但Neptune可以打印正确的数字但为负数。有人告诉我要把双打放长一点，但是我相信我已经做到了，而且没有任何区别。任何帮助或指导，将不胜感激。我将附上我的代码，以便你们看看。另一件事是，当海王星被选择为“h”时，假设选择为“h”，则体重为160，速度为595。此外，应该以小时为单位打印的旅行时间为4537815，第189076天和年是518.02。正确显示小时和天数，只是在我的代码中最后一个数字需要四舍五入，而正确显示年数，只是它是负数。
#include <iostream>
#include <iomanip>
#include <cmath>
#include <string>
using namespace std;
int main()
{
char selection;
double weight = 0.0;
double speed = 0.0;
double surfGrav;
double distEarthToSun = 93 * 1000000;
double distfromSun = 0.0;
double newSunDist;
double newWeight;
double distFromPlanets;
// double travelTime;
double travelTimeHours;
double travelTimeDays;
double travelTimeYears;
string planetName;
cout << "Welcome to INTERPLANETARY TRAVEL PROGRAM!\n";
cout << "This program enables you to find out your travel time to the planet\n"
<< "you want to travel to as well as your weight on that planet.\n";
cout << "Please enjoy the program and find the perfect planet for you!\n";
cout << '\n';
cout << '\n';
cout << "INTERPLANETARY TRAVEL MENU\n";
cout << "--------------------------\n";
cout << "a) Mercury\n";
cout << "b) Venus\n";
cout << "c) Earth\n";
cout << "d) Mars\n";
cout << "e) Jupiter\n";
cout << "f) Saturn\n";
cout << "g) Uranus\n";
cout << "h) Neptune\n";
cout << "q) quit\n";
cout << '\n';
cout << "Select a planet to travel to or q to quit the program: \n";
cin >> selection;
if (selection >= 'a' && selection <= 'h')
{
cout << "Please enter your weight (in lbs): \n";
cin >> weight;
cout << "Please enter the speed (in mile per hour) that you would like to travel at: \n";
cin >> speed;
}
if (selection == 'a')
{
planetName = "Mercury";
surfGrav = 0.27;
distfromSun = 36;
}
else if (selection == 'b')
{
planetName = "Venus";
surfGrav = 0.86;
distfromSun = 67;
}
else if (selection == 'c')
{
planetName = "Earth";
surfGrav = 1.00;
distfromSun = 93;
}
else if (selection == 'd')
{
planetName = "Mars";
surfGrav = 0.37;
distfromSun = 141;
}
else if (selection == 'e')
{
planetName = "Jupiter";
surfGrav = 2.64;
distfromSun = 483;
}
else if (selection == 'f')
{
planetName = "Saturn";
surfGrav = 1.17;
distfromSun = 886;
}
else if (selection == 'g')
{
planetName = "Uranus";
surfGrav = 0.92;
distfromSun = 1782;
}
else if (selection == 'h')
{
planetName = "Neptune";
surfGrav = 1.44;
distfromSun = 2793;
}
else if (selection == 'q')
{
cout << "You have chosen to quit the program. Thank you for using the program!\n";
return 0;
}
else
{
cout << "You have entered an invalid selection.\n";
return 0;
}
newWeight = weight * surfGrav;
newSunDist = distfromSun * 1000000;
unsigned long l1 = newSunDist;
if (selection <= 'a' || selection >= 'h')
{
distFromPlanets = distEarthToSun - l1;
}
else
{
distFromPlanets = l1 - distEarthToSun;
}
travelTimeHours = distFromPlanets/speed;
travelTimeDays = travelTimeHours/24.0;
travelTimeYears = travelTimeDays/365.0;
cout <<'\n';
cout << "INTERPLANETARY TRAVEL: Earth to " << planetName << '\n';
cout << "--------------------------------------------------\n";
cout << fixed << setprecision(2) << "Your weight on " << planetName << ": " << newWeight << " lbs\n";
cout << '\n';
cout << "Your travel time to " << planetName << ":\n";
cout << fixed << setprecision(2) << " " << "In Hours: " << (long int)(travelTimeHours + 0.5) << " hours\n";
cout << fixed << setprecision(2) << " " << "In Days : " << (long int)(travelTimeDays + 0.5) << " days\n";
cout << fixed << setprecision(2) << " " << "In Years : " << travelTimeYears << " years\n";
cout << '\n';
return 0;
}
感谢您提前提供的帮助，如果您需要更多信息，请告诉我。谢谢。
最佳答案
问题出现在您的变量distFromPlanets，它解析为-2.7e + 9，分别是distEarthToSun = 9.3e+7和newSunDist = 2.8e+9。因此，9.3e+7 - 2.8e+9大约等于-2.8e+9。我不是天文学家，但是如果您将if语句更改为if(selection <= 'a' || selection > 'h')，则Neptune的计算将解析为2.8e+9 - 9.3+7 ~ +2.7e+9。同样，我不是天文学家，所以我不确定这是否是您应该计算的。
关于c++ - 将double转换为无符号长C++，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/29054099/