class AliStrLine: public TObject

 Default constructor

 Standard constructor
 if twopoints is true:  point and cd are the 3D coordinates of
                        two points defininig the straight line
 if twopoint is false: point represents the 3D coordinates of a point
                       belonging to the straight line and cd is the
                       direction in space

 Standard constructor
 if twopoints is true:  point and cd are the 3D coordinates of
                        two points defininig the straight line
 if twopoint is false: point represents the 3D coordinates of a point
                       belonging to the straight line and cd is the
                       direction in space

 Standard constructor
 if twopoints is true:  point and cd are the 3D coordinates of
                        two points defininig the straight line
 if twopoint is false: point represents the 3D coordinates of a point
                       belonging to the straight line and cd is the
                       direction in space

 copy constructor

 Assignment operator

 Getter for weighting matrix, as a [9] dim. array

 Setter for weighting matrix, strating from a [9] dim. array

 Initialization from a point and a direction

 Initialization from the coordinates of two
 points in the space

 destructor

 Print current status

 returns 1 if lines are parallel, 0 if not paralel

 Cross 2 lines in the X-Y plane

 Looks for the crossing point estimated starting from the
 DCA segment

Returns the distance of closest approach between two lines

 Fills the array point with the current value on the line

 computes distance from point

 Input: radial distance from the origin (x=0, x=0) in the bending plane
 Returns a boolean: kTRUE if the line crosses the cylinder of radius r
 and axis coincident with the z axis. It returns kFALSE otherwise
 Output: t1 and t2 in ascending order. The parameters of the line at
 the two intersections with the cylinder