// Source: "Software Design ...", John A Robinson, Newnes, 2004, page 126.
//
// Prints out zones of locations in a location database. Format of the database is:
// First line: Integer number of records
// Remaining lines: One record per line: Loc name (20 chars max), latitude, 
// ns character modifier for latitude,
// longitude, ew character modifier for longitude 

// fstream required because file input/output streams are used
#include <fstream>
#include <iostream>
using namespace std;

// An enumerated type is created to associate meaningful names with the index values of 
// the zones array immediately below:
enum { nfrigid, ntemperate, torrid, stemperate, sfrigid, error };

// The zones array is simply static array of pointers to constant strings that
// specify names of the Earth's zones.
const char *zones[6] = {
      "North frigid",
      "North temperate",
      "Torrid",
      "South temperate",
      "South frigid",
      "None"         // Flag to indicate error return
      };

// Now follows the definition of the location class. Most of the functions are defined 
// inside because they are short. Only member function zone is long enough to have its 
// definition outside the class definition

class location {
      char name[20];
      float latitude; char ns;
      float longitude; char ew;
public:
       location() {};  		// Null constructor - nothing to initialize
       ~location() {};		// Null destructor - nothing to tidy up on destruction
       void load(istream& in)	// Load data items from an input istream object.
				// This will usually be a file (and is in the main
				// program below), but it could be cin
            {
            in >> name >> latitude >> ns >> longitude >> ew;
            }
       void save(ostream& out) const  	// Save data items to output stream object
					// (usually a file)
					// Not used in this example
            {
            out << name << ' ' << latitude << ' ' << ns << ' '
                << longitude << ' ' << ew << '\n';
            }
       const char *getname() const
            {
            return(name);
            }
       const char *zone() const;// Large member function - defined outside class defn.
       };

// The member function *zone() was declared inside the location class definition, but not
// defined. Here is its definition:
// The zone member function returns a pointer to a string stating which zone of the earth
// this particular place is located 
const char *location::zone() const
      {
      if (!name[0])       		// No location loaded in this object
            return zones[error]; 	// Error return
      if (latitude < 23.5)
            return zones[torrid];	// Using the values of enum to index the zones array
      if (latitude < 66.5)
            {
            if (ns == 'N')
                  return zones[ntemperate];
            return zones[stemperate];
            }
      if (ns == 'N')
             return zones[nfrigid];
      return zones[sfrigid];
      }

//
// Here is the main program which uses a location object to read in locations from a
// database one by one, and print out their zones.
//
int main(int argc, char *argv[])
    {
    if (argc != 2) {
       cout << "Usage: tellzone locationsfile\n";
       return -1;
       }
    ifstream infile(argv[1]);		// Opening the file specified on the command line as an
					// input file stream object
    if (!infile)   {
       cerr << "Can't open " << argv[1] << " for reading\n";
       return -1;
       }
    int numrecords;
    infile >> numrecords;		// The first line of the database contains a single number
					// specifying the number of lines or "records" in the file
    location current_location;
    for (int i = 0; i < numrecords; i++)
        {
        current_location.load(infile);	// Load the next line of infile into the
					// current_location object
        cout << "Location " << current_location.getname()
             << " is in the " << current_location.zone() << " zone\n";
        }
    infile.close();		// Close the file input stream when all lines are read
    return 1;
    }