public PlaDirection(PlaPointInt p_a,PlaPointInt p_b){
  this(BigInteger.valueOf(p_b.v_x - p_a.v_x),BigInteger.valueOf(p_b.v_y - p_a.v_y));
}

public PlaDirection ( PlaPointInt p_a , PlaPointInt p_b ) { this ( BigInteger . valueOf ( p_b . v_x - p_a . v_x ) , BigInteger . valueOf ( p_b . v_y - p_a . v_y ) ) ; }
the two points define a " line " and i want a direction of that to get it , you simply " move p_b so it is actually centered at zero with reference p_a the resulting value should be " reduced " note that the result may be a nan if the point are the same \
