Thread: Problem using overloaded << operator

Hello,

I am currently creating a class to represent a PolyLine. I have all my methods working correctly, but I need to make an overloaded << operator. Here is the method I am using for testing purposes:

Code:

void output() {
        int finalSpot = length - 1;
        for (int i = 0; i < finalSpot; i++)
                cout << "(" << x[i] << "," << y[i] << "):";
                
        cout << "(" << x[finalSpot] << "," << y[finalSpot] << ")" << endl;
    }

The x and y arrays are variables of the PolyLine. They are declared as follows in my class:

Code:

   double *x;
    double *y;

What would the ostream method equivalent of my output method be? I've tried a number of things and none of them worked. Can someone please help me? Thanks.

I'm still getting errors when I try to compile. Here is my entire code for the class as it stands right now:

Code:

#include <iostream>
using namespace std;

class PolyLine {
    double *x;
    double *y;
    int length;
    
  public:
    PolyLine (double xVals[], double yVals[], int num) {
        length = num;
        x = new double[length];
        y = new double[length];
        
        for (int i = 0; i < length; i++) {
                x[i] = xVals[i];
                y[i] = yVals[i];
        }
    }
    
    int points() {
        return length;
    }
    
    double value(double xNum) {
        double val = 0.0;
        double finalSpot = x[length - 1];
		
        if (xNum < x[0] || xNum > finalSpot) return val;
		
        for (int i = 0; i < length; i++) {
            if (x[i] == xNum) val = y[i];
            else if (x[i] != xNum && x[i] > xNum) val = xNum;
        }
		
        return val;
    }
    
    double max() {
        double max = 0.0;
		
        for (int i = 0; i < length; i++)
            if (y[i] > max) max = y[i];
		
        return max;
    }
    
    double max(double a, double b) {
        double max = 0.0;
        double finalSpot = x[length - 1];
        int i = 0;
		
        while (x[i] != a) {
            if (i == length - 1) return max;
            else if (x[i] > a) {
               if (y[i] < 0) break;
               else {
                 max = y[i];
                 break;
               }
            }
            else i++;
        }
		
        while (x[i] != b) {
            if (i == length - 1 || x[i] > finalSpot || b < x[i]) return max;
            else if (y[i] > max) max = y[i];
            i++;
        }
		
        return max;	
    }
    
    double integral(double a, double b) {
        double integ = 0.0;
        double trapFormula = 0.0;
        int i = 0;
        int num = 0;
		
        while (x[i] != a) {
            if (i == length - 1) return integ;
            else i++;
        }
		
        while (x[i] != b && i != length - 1) {
            trapFormula = ((x[i+1] - x[i]))*((y[i]+y[i+1])/2);
            integ += trapFormula;
            i++;
        }
		
        return integ;
		
    }
    
    ostream output(ostream &out) {
        int finalSpot = length - 1;
        for (int i = 0; i < finalSpot; i++)
                out << "(" << x[i] << "," << y[i] << "):";
                
        out << "(" << x[finalSpot] << "," << y[finalSpot] << ")" << endl;
        return out;
    }
    
    ostream & operator << (ostream & out, const PolyLine ob) {
        return ob.output(out);
    }
};

Can you tell me what I'm doing wrong now? Thanks.

try this:

Code:

#include <iostream>
using namespace std;

class PolyLine {
    double *x;
    double *y;
    int length;
    
  public:
    PolyLine (double xVals[], double yVals[], int num) {
        length = num;
        x = new double[length];
        y = new double[length];
        
        for (int i = 0; i < length; i++) {
                x[i] = xVals[i];
                y[i] = yVals[i];
        }
    }
    
    int points() {
        return length;
    }
    
    double value(double xNum) {
        double val = 0.0;
        double finalSpot = x[length - 1];
		
        if (xNum < x[0] || xNum > finalSpot) return val;
		
        for (int i = 0; i < length; i++) {
            if (x[i] == xNum) val = y[i];
            else if (x[i] != xNum && x[i] > xNum) val = xNum;
        }
		
        return val;
    }
    
    double max() {
        double max = 0.0;
		
        for (int i = 0; i < length; i++)
            if (y[i] > max) max = y[i];
		
        return max;
    }
    
    double max(double a, double b) {
        double max = 0.0;
        double finalSpot = x[length - 1];
        int i = 0;
		
        while (x[i] != a) {
            if (i == length - 1) return max;
            else if (x[i] > a) {
               if (y[i] < 0) break;
               else {
                 max = y[i];
                 break;
               }
            }
            else i++;
        }
		
        while (x[i] != b) {
            if (i == length - 1 || x[i] > finalSpot || b < x[i]) return max;
            else if (y[i] > max) max = y[i];
            i++;
        }
		
        return max;	
    }
    
    double integral(double a, double b) {
        double integ = 0.0;
        double trapFormula = 0.0;
        int i = 0;
        int num = 0;
		
        while (x[i] != a) {
            if (i == length - 1) return integ;
            else i++;
        }
		
        while (x[i] != b && i != length - 1) {
            trapFormula = ((x[i+1] - x[i]))*((y[i]+y[i+1])/2);
            integ += trapFormula;
            i++;
        }
		
        return integ;
		
    }
    
  friend  ostream& operator <<(ostream &out, const PolyLine& ob) {
        int finalSpot = ob.length - 1;
        for (int i = 0; i < finalSpot; i++)
                out << "(" << ob.x[i] << "," << ob.y[i] << "):";
                
        out << "(" << ob.x[finalSpot] << "," << ob.y[finalSpot] << ")" << endl;
        return out;
    }
    
};

There we go, that did it! Thanks for the help.

Sorry I forgot an & in my code. The return for output should be a reference to an object and not an object itself. Code has been updated. Btw in the future you may want to include the errors instead of just saying you have errors.