c++ putting objects into arrays -

i trying make city distance calculator using longitude , latitude of city. problem having putting cities array. array attempt commented out in main method. please let me know doing wrong.

#include <iostream> #include <math.h> #define pi 3.14159265358979323846  using namespace std;  double distance(double lat1, double lon1, double lat2, double lon2, char unit); double deg2rad(double deg); double rad2deg(double rad);  class city { public:     //declare variables     string name;     double latitude;     double longitude;      city(string, double, double); //constructor     double distance(string, string); };  double citydistance(city a, city b);  int main() {      //construct cities     city providence("providence", 41.8239890, -71.4128340);     city cranston("cranston", 41.7798230, -71.4372800);     city newyork("newyork", 40.7143530, -74.0059730);     city boston("boston", 42.3584310, -71.0597730);     city killington("killington", 43.6775680, -72.7798250);     city springfield("springfield", 42.1014830, -72.5898110);     city bridgeport("bridgeport", 41.1865480, -73.1951770);     city cambridge("cambridge", 42.3736160, -71.1097340);     city norwalk("norwalk", 41.1175970, -73.4078970);     city quincy("quincy", 42.2528770, -71.0022710);      //put city array //  city cityarray[] = { }; //  cityarray[0] = {"providence", 41.8239890, -71.4128340}; //  cityarray[1] = {"cranston", 41.7798230, -71.4372800}; //  cityarray[2] = {"newyork", 40.7143530, -74.0059730}; //  cityarray[3] = {"boston", 42.3584310, -71.0597730}; //  cityarray[4] = {"killington", 43.6775680, -72.7798250}; //  cityarray[5] = {"springfield", 42.1014830, -72.5898110}; //  cityarray[6] = {"bridgeport", 41.1865480, -73.1951770}; //  cityarray[7] = {"cambridge", 42.3736160, -71.1097340}; //  cityarray[8] = {"norwalk", 41.1175970, -73.4078970}; //  cityarray[9] = {"quincy", 42.2528770, -71.0022710};      //calculate distance     cout << "distance between providence , cranston: " << distance(41.8239890, -71.4128340, 41.7798230, -71.4372800, 'm') << endl;     cout << "distance between newyork , boston: " << distance(40.7143530, -74.0059730, 42.3584310, -71.0597730, 'm') << endl;     cout << "distance between killington , norwalk: " << distance(43.6775680, -72.7798250, 41.1175970, -73.4078970, 'm') << endl;      //print distance using city name     cout << endl;     cout << "distance between providence , cranston: " << citydistance(providence, cranston) << endl;     cout << "distance between newyork , boston: " << citydistance(newyork, boston) << endl;     cout << "distance between killington , norwalk: " << citydistance(killington, norwalk) << endl;      //end     return 0; }  city::city(string n, double lt, double lg) {     name = n;     latitude = lt;     longitude = lg; }  double deg2rad(double deg) {     return (deg * pi / 180); }  double rad2deg(double rad) {       return (rad * 180 / pi); }  double distance(double lat1, double lon1, double lat2, double lon2, char unit) {     double theta, dist;     theta = lon1 - lon2;     dist = sin(deg2rad(lat1)) * sin(deg2rad(lat2)) + cos(deg2rad(lat1)) * cos(deg2rad(lat2)) * cos(deg2rad(theta));     dist = acos(dist);     dist = rad2deg(dist);     dist = dist * 60 * 1.1515;     switch(unit) {         case 'm':             break;         case 'k':             dist = dist * 1.609344;             break;         case 'n':             dist = dist * 0.8684;             break;       }       return(dist); }   double citydistance(city a, city b) {     return distance(a.latitude, a.longitude, b.latitude, b.longitude, 'm'); } 

this great example of when use std::vector or std::map. in particular case, think std::map better choice (since wouldn't have iterate entire list find 2 cities looking for):

std::map<std::string, city> cities; cities["providence"] = city("providence", 41.8239890, -71.4128340); // ... 

example