query/ignore and use of Ferret error messages

[Emilie Vanvyve <vanvyve@xxxxxxxxxxxxxx>]

Hello,

1. I was wondering if there is any way to simultaneously  check the value of an optional argument of a script, display an error message if wrong, and attribute it a default value if undefined, i.e. to do in 1 line this serie of commands:

define symbol orientation = ($1%portrait%)  !orientation can be "portrait" (default) or "landscape", nothing else.
if ($orientation"|portrait>F|landscape>F|*>T|") then
say "$&@# usage: go my_script [portrait/landscape]"
exit
endif
...

I was thinking to something like:

query/ignore $1%portrait|portrait|landscape|<$&@# usage: go my_script [portrait/landscape]%

but then, when $1 is supposed to have been set by default to its default value (because not provided by the user), I can not use $1 in:

say ($1) or  Fprint -l ($1)
=> I get the error message " **ERROR: invalid command: Value needed for argument 1 in command"

The command query/ignore understood the default value instruction but does not seem to have attributed it to $1 (that's maybe not its function too).
I just would like to avoid to have ($1"...|...|...|") everywhere in my script. Just one would be enough. I probably can do this:

query/ignore $1%portrait|portrait|landscape|<$&@# usage: go my_script [portrait/landscape]%
define symbol orientation = ($1%portrait%)

but maybe is there a way to do is still shortly.

2. Last short question: is it possible to use and "customize" the error messages usually given by Ferret? So, automatically have this kind of message when a script encounters an error (error defined by me, not a normal error of Ferret): **ERROR: my error message
Is there any "error code", like 0 => ok, 1 => **ERROR:, 2 => *** NOTE:, ... ?

Thanks for any help!

Emilie

____________________________________________________________
Emilie VANVYVE
Physicist, PhD student

Université catholique de Louvain (UCL)
Institut d'astronomie et de géophysique G. Lemaître (ASTR)
Chemin du Cyclotron, 2
1348 Louvain-la-Neuve (Belgium)
Phone : +32-(0)10-473300
Fax : +32-(0)10-474722
E-mail : vanvyve@astr.ucl.ac.be
Web : www.astr.ucl.ac.be