Re: [babel] Suggestions: GRASS GIS und Lilypond

[Rainer M Krug <r.m.krug@gmail.com>]

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On 02/15/2011 07:46 PM, Eric Schulte wrote:
> I am happy to answer questions and provide suggestions for anyone who is
> interested in developing support for these (or any other) additional
> languages.  I would recommend looking at existing languages which are
> similar to the new language for guidance/examples.
> 
> In the case of GRASS, it sounds as though GRASS is a sub[super]-set of
> R?  

No - GRASS can be described as a collection of commands which are
executed in the shell after some environmental variables are set. So
GRASS is rather a super set of a bash shell.
So an implementation of GRASS could easily build on how sh code blocks
are hab=ndled in org.

Interactive GRASS sessions are effectively sh sessions with adapted
$PATH variable and a few environmental variables, to make the GRASS
commands accessible. So really the easiest would be to use the existing
sh support, set the environmental variables, set the $PATH and execute
the commands.
The environmental variables could be defined in :var - so actually that
should not be a problem.

Syntax highlighting could be based on sh with added commands in the
added $PATH - should not be to difficult (theoretically...).

> Would it be possible to simply use the existing R support in babel
> only specify a non-R command to be run to start interactive sessions?

Well - R, like python which is becoming the "official" scripting
language for GRASS, has a set of commands to interface with GRASS - so
using R (or python) would not be a useful approach.

There is an R package (spGRASS6) which is doing exactly what I mentioned
above (setting the $PATH and the environmental variables) to be able to
execute grass commands from within R - (with the syntax

execGRASS( "COMMAND", ... )

So one could look at that command (initGRASS() I think it is called) to
see what is necessary - or just execute grass:

grass -text GISBASE/LOCATION_NAME/MAPSET

##########################################
rkrug@ecolmod:~/deb$ grass --help
Usage:
  grass64 [-h | -help | --help] [-v | --version] [-c]
          [-text | -gui | -tcltk | -oldtcltk | -wxpython | -wx]
          [[[<GISDBASE>/]<LOCATION_NAME>/]<MAPSET>]

Flags:
  -h or -help or --help          print this help message
  -v or --version                show version information and exit
  -c                             create given mapset if it doesn't exist
  -text                          use text based interface
                                   and set as default
  -gui                           use graphical user interface (wxpython
by default)
                                   and set as default
  -tcltk                         use Tcl/Tk based graphical user interface
                                   and set as default
  -oldtcltk                      use old Tcl/Tk based graphical user
interface
                                   and set as default
  -wxpython or -wx               use wxPython based graphical user interface
                                   and set as default

Parameters:
  GISDBASE                       initial database (path to GIS data)
  LOCATION_NAME                  initial location
  MAPSET                         initial mapset

  GISDBASE/LOCATION_NAME/MAPSET  fully qualified initial mapset directory

Environment variables relevant for startup:
  GRASS_GUI                      select GUI (text, gui, tcltk, oldtcltk,
wxpython)
  GRASS_TCLSH                    set tclsh shell name to override 'tclsh'
  GRASS_WISH                     set wish shell name to override 'wish'
  GRASS_HTML_BROWSER             set html web browser for help pages
  GRASS_ADDON_PATH               set additional path(s) to local GRASS
modules
  GRASS_BATCH_JOB                shell script to be processed as batch job
  GRASS_PYTHON                   set python shell name to override 'python'
rkrug@ecolmod:~/deb$
##########################################


So it should be doable relatively easily I guess.

So the environmental variables needed would be:

 GISDBASE                    initial database (path to GIS data)
 LOCATION_NAME               initial location
 MAPSET                      initial mapset

So that GRASS can build

 GISDBASE/LOCATION_NAME/MAPSET  fully qualified initial mapset directory

Thinking of it, a GRASS code block

#+begin_src grass
 ...
#+end_src

would be a sh code block, in which as the first command "grass -text" is
executed, i.e.

#+begin_src grass
  grass -text
  ...
#+end_src

For tangling: GRASS scripts are executed usually from within GRASS, so
they are normal sh scripts (same shebang and all)

So implementation should be rather straight forward, I think?

Just a side note: as GRASS installs in addition to the command grass
also a command "grass64" for version 6.4 etc, it would be nice to have
the command "grass" modifiable.


Cheers,

Rainer

> 
> Best -- Eric
> 
> Thorsten  <gruenderteam.berlin@googlemail.com> writes:
> 
>> Hello Babel developers, 
>> just two suggestions for new languages: 
>> 1. GRASS GIS
>> As far as I know there is no grass-mode in emacs, but some expert people are
>> successful running grass processes together with R processes in ESS.
>> Since GRASS and R are natural allies, it would be great to use the GRASS
>> engine in an org-file to retrieve spatial data and then analyse the data
>> with R in the same file - would make Org a kind of emacs-grassmode
>> replacement.  
>> 2. Lilypond
>> A nice to have for all the music lovers in the org community. 
>> Regards
>> Thorsten
>>
>>
>> _______________________________________________
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> 
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- -- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

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