public PlaDirection(PlaVectorInt p_vector){
  this(BigInteger.valueOf(p_vector.v_x),BigInteger.valueOf(p_vector.v_y));
}

public PlaDirection ( PlaVectorInt p_vector ) { this ( BigInteger . valueOf ( p_vector . v_x ) , BigInteger . valueOf ( p_vector . v_y ) ) ; }
construct a direction from an intvector , an int vector is already centered at zero one key point is to " reduce " the points using the gcd
