TDPRPI - Given a point in the projection plane, retrieve the parallelogram coordinates of that point in

       To  use TDPRPI or c_tdprpi, load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in
       that order.

       The C-binding argument descriptions are the same as the FORTRAN argument descriptions.

       #include <ncarg/ncargC.h>

       void c_tdprpi(float xi2d, float yi2d, float *xipa, float *yipa)

       Copyright (C) 1987-2009
       University Corporation for Atmospheric Research
       The use of this Software is governed by a License Agreement.

UNIX                                                July 1997                                     TDPRPI(3NCARG)

       The arguments of TDPRPI are as follows:

       XI2D and YI2D
               (input expressions of type REAL) - the coordinates of a point in the projection plane.

       XIPA and YIPA
               (output  variables  of  type REAL) - the parallelogram coordinates of that point in the reference
               parallelogram that projects into (XI2D,YI2D).  (The parallelogram is as defined by a  prior  call
               to TDPARA.)

       TDPRPI - Given a point in the projection plane, retrieve the parallelogram coordinates of that point in
       the reference parallelogram (as defined by the last call to TDPARA) that projects into it.  This routine
       is essentially the inverse of the routine TDPRPA.

       Online: tdclrs, tdctri, tddtri, tdgeti, tdgetr, tdgrds, tdgrid, tdgtrs, tdinit, tditri,  tdlbla,  tdlbls,
       tdline,  tdlnpa,  tdmtri,  tdotri, tdpack, tdpack_params, tdpara, tdplch, tdprpa, tdprpt, tdseti, tdsetr,
       tdsort, tdstri, tdstrs

       CALL TDPRPI (XI2D, YI2D, XIPA, YIPA)