///////    File rect.C    ///////
#include <iostream.h>
#include "Vector.h"

inline float ABS(float x)
       { return(x > 0 ? x : -x); }

int perpendicular(Vector& a, Vector& b)
{   return ( a.inner(a) > 0 && b.inner(b) > 0
             && ABS(a.inner(b)) < 0.00000001 );
}

void getpoint(float& x, float& y, int i)
{   cout << "x" << i << "= ";
    cin >> x;
    cout << "y" << i << "= ";
    cin >> y;
}

int main()
{  cout << "Enter vertices 0, 1,2,3 \n";
   float x[4], y[4];
   for ( int i = 0; i < 4; i++)
       getpoint(x[i], y[i], i);
   Vector u(x[1]-x[0], y[1]-y[0]);
   Vector v; 
   for ( i = 0; i < 3; i++)
   {  v = Vector(x[(i+2)%4]-x[i+1], y[(i+2)%4]-y[i+1]);
      if ( ! perpendicular(u, v) )
      {   cout << "No, not a rectangle.\n";
          return(0);
      }
      u = v;
   }
   cout << "Yes, a rectangle.\n";
   return(0);
}