c++ - 计算器程序错误

Question

我正在使用一个程序来计算地球表面两个地理点之间的距离。我是 C++ 的新手，如果我的英语不好，我深表歉意

关于如何将程序底部的内容正确无误地导入顶部程序，有什么建议吗？

这是不起作用的程序。

   #include <iostream>
   #include <cstdio>
   #include <cmath>
   using namespace std;

    int main ()
    double getdistance(double x1,double y1,double x2,double y2)
    {

        const double PI = 3.1415927; 
        double radius, sum; 
        int exit = 1;
        char choice;
        while (exit == 1)
    {

        cout    << "**** Calculate Program **** \n\n"
                << "1. Volume\n"
                << "2. Div\n"
                << "3. Calculate two geographical points\n"
                << "4. Working\n\n"
                << "5. Quit program\n\n";

        cout    << "Choose one of the options and write it here: "; 
        cin     >> choice; 

switch (choice) 
    {
    // 
    case '1':   
        float volume (float radius);               
    {
            cout << "radius you want to calculate: " << endl;
            cin >> radius;
            sum = 4.0/3.0 * PI * pow (radius, 3);
            cout << "Volume: " << sum << endl;
    }

    break;


    // 
    case '2':   
        cout<<"div \n"; 
            break;
    // 
    case '3':   

        radius=6371; // radius km
        double pi=3.14159265;
        double x1,y1,x2,y2;
        // X og Y coords
            x1=(x1/180)*pi; 
            y1=(y1/180)*pi;
            x2=(x2/180)*pi;
            y2=(y2/180)*pi;

         // if else
            if (x1==x2 && y1==y2)
            return 0;
            else
        {
            if ((sin(x2)*sin(x1)+cos(x2)*cos(x1)*cos(y2-y1))>1)
             return radius*acos(1.0);
            else
            return radius*acos(sin(x2)*sin(x1)+cos(x2)*cos(x1)*cos(y2-y1));


            // 

            double x1,y1,x2,y2;
            cout<<"Write the coords you like to calculate distance from: \n";
            cin>>x1>>y1;
            cin>>x2>>y2;
            cout<<"distance in km : \n";
            cout<<getdistance(x1,y1,x2,y2)<<endl;
            return 0;
        }

    break;


    case '4':   
        cout<<"working \n"; 
    break;


    // 
    case '5':   
            exit = 0;
    break;
    default: 
            exit = 0;
            cout << "ERROR!";
     }  // Switch quit

} // While quit
return 0;
}

这是有效的程序，但我必须将它放在上面程序的案例 3 中。

# include <iostream>
# include <cstdio>
# include <cmath>

using namespace std;

double getdistance(double x1,double y1,double x2,double y2)
{
    double radius;
    radius=6371; // radius km
    double pi=3.14159265;

    // X og Y coord
    x1=(x1/180)*pi; 
    y1=(y1/180)*pi;
    x2=(x2/180)*pi;
    y2=(y2/180)*pi;


    if (x1==x2 && y1==y2)
        return 0;
    else
    {
       if ((sin(x2)*sin(x1)+cos(x2)*cos(x1)*cos(y2-y1))>1)
           return radius*acos(1.0);
       else
           return radius*acos(sin(x2)*sin(x1)+cos(x2)*cos(x1)*cos(y2-y1));
    }
}
int main()
{

    double x1,y1,x2,y2;
    cout<<"Write the coords you like to calculate distance from: \n";
    cin>>x1>>y1;
    cin>>x2>>y2;
    cout<<"distance in km : \n";
    cout<<getdistance(x1,y1,x2,y2)<<endl;
    return 0;
}

Answer 1

程序看起来不错。至于 switch 语句，它们只适用于整数或单个字符值。 switch 不比较字符串或 float 。也许发布您的替代方案的完整代码将有助于确定问题。

编辑

int main ()
double getdistance(double x1,double y1,double x2,double y2)
{

这是错误的。当你声明函数时，你必须在 before main 之前声明它们，并在 main 之前或之后定义它们，尽管通常你会在 after.

即

//#include directives

double getdistance(double x1,double y1,double x2,double y2);

int main() {
// code for main()
}

double getdistance(double x1,double y1,double x2,double y2) {
//code for your function
}