Homework Help

[AlexanderGreen]

My assignment is to read a file, skipping the first two lines, and given three commands START, DATA, and STOP, I must calculate total distance traveled and the distance between the start and stopping points. START and STOP both indicate that the next two values are the beginning x and y coordinates or the ending x and y coordinates. The DATA command just indicates a new x and y coordinate.

My text file I'm reading looks like this:

GPS Data File
Command x-coordinate y-coordinate
START 0 0
DATA 24 24
DATA 4 24
DATA 4 124
DATA -25 12
DATA 0 0
STOP 195 215

For some reason, if I don't have the first two lines there and I just have data immediately on the first line, my code works. Why is my program not skipping these first two lines?

#include <iostream>
#include <fstream>    //For ofstream and ifstream variables
#include <cmath>      //For sqrt(), pow()
#include <iomanip>    //For fixed, showpoint, setprecision
#include <string>     //For string objects

using namespace std;

int main()
{

  //Data Abstraction:

  double x_start        = 0.0,
         x_end          = 0.0,
         x_data_1       = 0.0,
         x_data_2       = 0.0,
         y_start        = 0.0,
         y_end          = 0.0,
         y_data_1       = 0.0,
         y_data_2       = 0.0,
         distance       = 0.0,
         total_distance = 0.0;

  int    attempts       = 0;

  string file_name;
  string command;
  ifstream in;
  ofstream out;


  //Input:

  do
  {

    cout << "Please Enter The Name Of The Data File: ";
    cin  >> file_name;
    in.open(file_name.c_str());

      if(!in.is_open() && attempts < 3)
        cout << "ERROR: File did NOT open - try again." << endl;

    attempts++;
  }
  while (!in.is_open() && attempts < 3);

  if(!in.is_open())
    cout << "\nERROR: File did NOT open in 3 attempts." << endl;

  //Open File and calculate distances

  else
  {
    in.ignore( 13, '\n' );
    in.ignore( 80, '\n' );

  //Reading File

      while (in >> command)
      {
          if (command == "START")
          {
            in >> x_start >> y_start;
            in >> command;

             if (command == "DATA")
             {
               in >> x_data_1 >> y_data_1;
               total_distance += sqrt(pow((x_data_1 - x_start), 2.0)
                               + pow((y_data_1 - y_start), 2.0));
             }

             else
             {
               in >> x_end >> y_end;
               total_distance += sqrt(pow((x_start - x_end), 2.0)
                              + pow((y_start - y_end), 2.0));
             }

          }

          if (command == "DATA")
          {
            in >> x_data_1 >> y_data_1;
            in >> command;

              if(command == "DATA")
              {
                in >> x_data_2 >> y_data_2;

                total_distance += sqrt(pow((x_data_2 - x_data_1), 2.0)
                                + pow((y_data_2 - y_data_1), 2.0));
              }

              else
              {
                in >> x_end >> y_end;

                total_distance += sqrt(pow((x_data_1 - x_end), 2.0)
                               + pow((y_data_1 - y_end), 2.0));
              }

          }

          if(command == "STOP")
          {
            in >> x_end >> y_end;

            total_distance += sqrt(pow((x_data_1 - x_end), 2.0)
                           + pow((y_data_1 - y_end), 2.0));
          }

      }

    distance += sqrt(pow((x_start - x_end), 2.0)
             + pow((y_start - y_end), 2.0));

  //Displaying Results to stdout and output file

    out.open("GPS.report.txt");
    cout << fixed << showpoint << setprecision(1);
    out  << fixed << showpoint << setprecision(1);

    cout << "\nFinal Location: " << "(" << x_end << ", "
         << y_end << ")" << endl;
    cout << "Total distance traveled: " << total_distance << endl;
    cout << "Distance to starting point " << distance << endl;

    out << "Final Location: " << "(" << x_end << ", "
        << y_end << ")" << endl;
    out << "Total distance traveled: " << total_distance << endl;
    out << "Distance to starting point " << distance;

    out.close();
    in.close();

  }

  return 0;

}

[coder777]

Well, it reads as if after each command there will be only a single pair of coordinates, but you always read four values. Why so?

[AlexanderGreen]

@coder777 oh shoot, thanks. What I was trying to do was get the next set of coordinates so I could use the distance formula to update total_distance. I think what's happening is that when it reads the next set of coordinates, it's actually reading the command on the next line.

How could I get it to where it reads the next set of data, then the next command, then the next coordinates and calculate?

[AlexanderGreen]

I updated my code but I'm still getting that funky read :/

[coder777]

You think to complicated. How about this:

      while (in >> command)
      {
          if (command == "START")
          {
            in >> x_start >> y_start;
            in >> x0 >> y0;
          }

          else if (command == "DATA")
          {
            in >> x1 >> y1;

                total_distance += sqrt(pow((x1 - x0), 2.0)
                               + pow((y1 - y0), 2.0));
            x0 = x1;
            y0 = y1;
          }

          else if(command == "STOP")
          {
            in >> x_end >> y_end;

            total_distance += sqrt(pow((x0 - x_end), 2.0)
                           + pow((y0 - y_end), 2.0));
          }

      }