return the x offset of this vector start to end point . concode_field_sep double dx concode_elem_sep double dy concode_elem_sep double length concode_elem_sep int direction concode_field_sep void add concode_elem_sep int getDirection concode_elem_sep void revertVertical concode_elem_sep void scale concode_elem_sep void setNeutral concode_elem_sep void updatePolar concode_elem_sep void setLength concode_elem_sep double getY concode_elem_sep double getLength concode_elem_sep Vector copy concode_elem_sep void setDirection concode_elem_sep void revertHorizontal concode_elem_sep void updateCartesian
double function ( ) { return dx ; }