如何打印我的功能的距离？

问题描述

我是C ++的新手。这是我的第一个任务，我在打印（在main()中）到函数d的最终计算距离getairdistance()时遇到了麻烦。我的程序如下所示，我将不胜感激！

#include <iostream>
#include <cmath> //for pi
using namespace std;
    
void getAirdistance(int *ptr,int *ptr1);
    
int main(){
    struct LOC{
        char loc_name[50]; //name of a location on earth
        double latitude; //latitude of this location
        double longitude; //longitude of this location
    }; //structure deFinition
    
    struct LOC location1;
    struct LOC location2; //declared two structures
    struct LOC *ptr,*ptr1; //declared two pointers
    ptr = &location1; //pointer to the first location structure
    ptr1 = &location2; //pointer to the second location structure
    
    cout << "Please enter the name of the first location: "; //print statement
    cin.getline(location1.loc_name,50);//use getline to store the first location
    cout << "Please enter the latitude (degrees): "; //print statement
    cin >> location1.latitude; //use cin to get the first latitude
    cout << "Please enter the longitude (degrees): "; //print statement
    cin >> location1.longitude; //use cin to get the first longitude
    
    fflush(stdin);
    
    cout << "Please enter the name of the second location: ";
    cin.getline(location2.loc_name,50);
    cout << "Please enter the latitude (degrees): ";
    cin >> location2.latitude;
    cout << "Please enter the longitude (degrees): ";
    cin >> location2.longitude; //exact same thing as above
    
    //getAirdistance(location1,location2);
    
    cout << "The air distance between " << location1.loc_name << " and " << location2.loc_name << " is appx. " << " km. "; //final print statement
}
    
void getAirdistance(int *ptr,int *ptr1){ //function deFinition
    double long1 = *(ptr + 2) * (M_PI/180); //longitude of first location (rad)
    double long2 = *(ptr1 + 2) * (M_PI/180); //longitude of second location (rad)
    double lat1 = *(ptr + 1) * (M_PI/180); //latitude of first location (rad)
    double lat2 = *(ptr1 + 1) * (M_PI/180); //longitude of first location (rad)
    double x = (long2 - long1) * cos((lat1 + lat2)/2); //x coordinate difference
    double y = lat2 - lat1; //y coordinate difference
    int R = 6371; //Radius of the earth
    int d = R * sqrt(pow(x,2) + pow(y,2)); //distance between the two locations
    cout << d;
}

解决方法

为调用者（即return）使函数d的值为main()，例如：

int getAirDistance(int *ptr,int *ptr1);
    
int main(){
    ...
    
    int d = getAirDistance(...);
    
    cout << ... << d << ...;

    return 0;
}
    
int getAirDistance(int *ptr,int *ptr1){
    ...
    int d = ...;
    return d;
}

---

话虽这么说，您的函数将int*指针作为输入，但是int代码中没有main()变量可以传递给函数。使用指针算术表明您认为+1和+2正在访问LOC结构的第一和第二字段，但这根本不会发生。我怀疑您真正打算做的是这样的事情：

#include <iostream>
#include <cmath> //for pi
using namespace std;
    
struct LOC{
    char loc_name[50]; //name of a location on earth
    double latitude; //latitude of this location
    double longitude; //longitude of this location
}; //structure definition

int getAirDistance(const LOC &loc1,const LOC &loc2);
    
int main(){
    LOC location1;
    LOC location2; //declared two structures
    
    cout << "Please enter the name of the first location: "; //print statement
    cin.getline(location1.loc_name,50);//use getline to store the first location
    cout << "Please enter the latitude (degrees): "; //print statement
    cin >> location1.latitude; //use cin to get the first latitude
    cout << "Please enter the longitude (degrees): "; //print statement
    cin >> location1.longitude; //use cin to get the first longitude
    
    fflush(stdin);
    
    cout << "Please enter the name of the second location: ";
    cin.getline(location2.loc_name,50);
    cout << "Please enter the latitude (degrees): ";
    cin >> location2.latitude;
    cout << "Please enter the longitude (degrees): ";
    cin >> location2.longitude; //exact same thing as above
    
    int d = getAirDistance(location1,location2);
    
    cout << "The air distance between " << location1.loc_name << " and " << location2.loc_name << " is appx. " << d << " km. "; //final print statement

    return 0;
}
    
int getAirDistance(const LOC &loc1,const LOC &loc2){ //function definition
    double long1 = loc1.longitude * (M_PI/180); //longitude of first location (rad)
    double long2 = loc2.longitude * (M_PI/180); //longitude of second location (rad)
    double lat1 = loc1.latitude * (M_PI/180); //latitude of first location (rad)
    double lat2 = loc2.latitude * (M_PI/180); //latitude of second location (rad)
    double x = (long2 - long1) * cos((lat1 + lat2)/2); //x coordinate difference
    double y = lat2 - lat1; //y coordinate difference
    int R = 6371; //Radius of the earth
    int d = R * sqrt(pow(x,2) + pow(y,2)); //distance between the two locations
    return d;
}