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UTRNR2

       SUBROUTINE  UTRNR2 (NORMAL,X,INCX,Y,INCY,N)
 C$    (Make Normals - 2-D)
 C$    Given a  2-D polygon  of N  vertices, no  adjacent pair  of
 C$    which are  coincident,  construct  and  return  the  inward
 C$    pointing unit normal  vectors, possibly for  use by one  of
 C$    the polygon clipping algorithms.  The polygon is assumed to
 C$    be ordered  such  that in  visiting  the vertices  1..N  in
 C$    order,  the  interior  always  lies  to  the  left  of  the
 C$    direction vector between  any vertex  pair.  The  arguments
 C$    are:
 C$
 C$    NORMAL(3,N)....Array of 2-D unit normals returned.
 C$    X(*)...........Array of X vertex coordinates.
 C$    INCX...........Increment between successive vertex entries
 C$                   in X(*).
 C$    Y(*)...........Array of Y vertex coordinates.
 C$    INCY...........Increment between successive vertex entries
 C$                   in Y(*).
 C$    N..............Number of vertices.
 C$
 C$    If INCX or INCY is negative, the starting point is taken as
 C$    (1-N)*INC + 1, so that  the corresponding array is  stepped
 C$    through in reverse order.
 C$    (21-MAR-83)