Question

My code in the colinear does not seem to work and its frustrating the hell out of me. Am i going the best way to use my line class by using two points in my point class? My test for colinearlirty is crashing so I am stuck in a rut for the past few days.

bool line::isColinear(line)
{
     bool line2=false;
     line l1,l2;

     if (l1.slope()==l2.slope())
     {
         if (l1.y_int()==l2.y_int())
         {
             line2 =true;
             return line2;
         }
     }
     else
     { 
         line2 =false;
     }

}

//Heres a copy of my line class

class line
{
    private:

    point p1,p2;

    public:

    bool isColinear(line);
    bool isParallel(line);
    point solve(line);
    double slope();
    double y_int();
    void  Display(ostream&);
};

Answer 1

1. You are storing line as between two points. Slope of a line is usually defined as

   slope = (y2 - y1) / ( x2 - x1 )

if x1 is equal to x2, you can have a division by zero error/exception.

Other things to be careful about

1. If you are storing point coordinates as integers, you could be doing just a integer division and not get what you expect
2. If you are using doubles throughout, please use a tolerance when comparing them