Author image Philippe Marguinaud

NAME

NCAR

SYNOPSIS

   use PDL;
   use NCAR;

   &NCAR::gopks( 6, 1 );
   &NCAR::gopwk( 1, 2, 1 );
   &NCAR::gacwk( 1 );

   #
   #  Symbolic station model
   #

   &NCAR::wmsetr('WBS',0.20);
   &NCAR::gslwsc(3.);

   ( ... )

   &NCAR::frame();
   &NCAR::gdawk( 1 );
   &NCAR::gclwk( 1 );
   &NCAR::gclks();

DESCRIPTION

Interfaces Perl, PDL & NCAR, through XS code. The aim is to provide the user with native NCAR commands.

Whenever large float/int arrays are needed, piddles have to be passed to NCAR routines, eg :

   my $F = float [ [ ... ], ... ];
   my $NX = ...;
   my $NY = ...;

   &NCAR::cpezct( $F, $NX, $NY );

Because the Fortran declaration of the routine cpezct looks like :

   C
         SUBROUTINE CPEZCT (ZDAT,MZDT,NZDT)
   C
         DIMENSION ZDAT(MZDT,NZDT)

However, small arrays ( ie arrays whose dimension is fixed and small ) are passed as native Perl ARRAY refs :

   &NCAR::mapset( "CO", [ 0., 0. ], [ -90., 0. ], [ 90., 0. ], [ 90., 0. ] );

Because the Fortran declaration of mapset is :

         SUBROUTINE MAPSET (ARG1,ARG2,ARG3,ARG4,ARG5)
         CHARACTER*(*) ARG1
         REAL          ARG2(2),ARG3(2),ARG4(2),ARG5(2)

So there is no need to use piddles in that case ( and it would not be very convenient ).

It is possible to pass arrays of strings :

   my @IMDAT = ( 
    '11212',
    '83320',
    '10011',
    '20000',
    '30000',
    '40147',
    '52028',
    '60111',
    '77060',
    '86792',
   );
   &NCAR::wmstnm($X2,.23, \@IMDAT);

Such arrays are converted into Fortran arrays of strings ( which is a rather dirty business ), and passed by value( up to now ), which means that you can't get back the modified values ( if the array was modified by the Fortran subroutine ).

Callbacks

Some NCAR Fortran subroutines accept callback subroutines as arguments, eg :

      EXTERNAL SHADER
      ( ... )
      CALL ARSCAM (IAMA,XCRA,YCRA,1000,IARA,IGRA,10,SHADER)
      ( ... )
      SUBROUTINE SHADER (XCS,YCS,NCS,IAI,IAG,NAI)

      END

It's possible to do that in Perl as wall, that is, one would write :

      &NCAR::arscam($IAMA,$XCRA,$YCRA,1000,$IARA,$IGRA,10,\&SHADER);
      ( ... )
      sub SHADER {
        my (XCS,YCS,NCS,IAI,IAG,NAI) = @_;
        ( ... )
      }

Common blocks

Some NCAR Fortran examples access COMMON blocks of the NCAR library, eg :

      COMMON /SRFIP1/ IFR        ,ISTP       ,IROTS      ,IDRX       ,
     1                IDRY       ,IDRZ       ,IUPPER     ,ISKIRT     ,
     2                NCLA       ,THETA      ,HSKIRT     ,CHI        ,
     3                CLO        ,CINC       ,ISPVAL
      ( ... )
      IFR = 0

In Perl, one would write :

      use NCAR::COMMON qw( %SRFIP1 );
      ( ... )
      $SRFIP1{IFR} = 0;

Note that only a few of the NCAR COMMON blocks have been included in NCAR.pm, although it would be possible to include them all ( there are about 280 of them in the NCAR library, so I will take a bit of time to consider which of them might be useful ).

User defined routines.

Some NCAR Fortran routines called from within the library may be re-defined by the user ( actually the whole library may be redefined by the user in Fortran :-); the following routines may ( according to their embedded documentation ) be overriden by the user :

  • agchax

  • agchnl

  • agchcu

  • agchil

  • agutol

  • cpchhl

  • cpchll

  • cpmpxy

  • mapeod

  • mapusr

  • mpchln

  • slubkg

  • vvumxy

In Perl, to override one of those routines, one would write :

      sub NCAR::mpchln {
        ( ... )
      }

for a permanent redefinition of mpchln, or :

      {
         local *NCAR::mpchln = sub {
           ( ... )
         };
         ( ... )
      }

for a local redefinition of mpchln.

Note that redefining a routine which is not part of the above mentioned set would not allow access to it from within the Fortran library.

BUILD

You need the full PDL package in order to build an use NCAR. Currently, the NCAR XS interface has only been tested on linux-i686 using the g77 compiler.

EXAMPLES

There's now quite a few examples ( converted by hand ) from the NCAR distribution. `make test' will execute them, and dump ncgm in the ncgm/ directory. ncgm files are viewable with the ctrans NCAR utility :

  ctrans -d X11 myplot.ncgm 
  ctrans -d ps.color myplot.ncgm > myplot.ps

BUGS

Maybe plenty of them !! Note that the XS glue includes the interfaces for more than 500 Fortran subroutines, and I haven't tested them all, though I have about 160 of the NCAR packages which seems to work fine.

SEE ALSO

  • NCAR graphics documentation ( http://ngwww.ucar.edu/ng4.3/ )

  • PDL documentation ( http://pdl.perl.org/ )

COPYRIGHT

Copyright (c) 2003 Philippe Marguinaud. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as the NCAR graphics library.

AUTHOR

Philippe Marguinaud, pmarguinaud@hotmail.com