public void minus( Point2D_F64 a , Point2D_F64 b ) {
		x = a.x - b.x;
		y = a.y - b.y;
	}
public void minus( Point2D_F64 a , Point2D_F64 b ) {
		x = a.x - b.x;
		y = a.y - b.y;
	}
public void minus ( Point2D_F64 a , Point2D_F64 b ) { x = a . x - b . x ; y = a . y - b . y ; }
In-place minus operation. this = a - b.

@param a Point
@param b Point
In - place minus operation . this = a - b .