#include "stdstuff.h"

#include "Vector.h"


Vector::Vector () {

  i = j = k = 0;

}


Vector::Vector (double i, double j, double k) {

  Vector::i = i; Vector::j = j; Vector::k = k;

}


double Vector::magnitude () const {

  return sqrt ((i * i) + (j * j) + (k * k));

}


double Vector::dot (const Vector &otherVector) const {

  return (i * otherVector.i) + (j * otherVector.j) + (k * otherVector.k);

}


Vector Vector::cross (const Vector &otherVector) const {

  Vector result;

  result.i = (j * otherVector.k) - (k * otherVector.j);
  result.j = (k * otherVector.i) - (i * otherVector.k);
  result.k = (i * otherVector.j) - (j * otherVector.i);

  return result;

}


void Vector::add (const Vector &otherVector) {

  i += otherVector.i; j += otherVector.j; k += otherVector.k;

}


void Vector::unitize () {

  // it would be a serious mistake to use magnitude in the /=
  // statemente.  the magnitude would change as we went along.
  double m = magnitude();

  if (m == 0) {
    throw domain_error ("cannot unitize zero vector");
  }
  
  i /= m; j /= m; k /= m;

}


void Vector::read (istream &is) {

  is >> i >> j >> k;

}


void Vector::write (ostream &os) {

  // this is ok but the below is nicer!
  // os << i << "i + " << j << "j + " << k << "k";

  os << i << "i ";
  if (j<0) {
      os << "- " << -j;
  } else {
      os << "+ " << j;
  }
  os << "j ";
  if (k<0) {
      os << "- " << -k;
  } else {
      os << "+ " << k;
  }
  os << "k";

}