| string definition question [message #33609] |
Tue, 14 January 2003 07:55 |
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Paul Van Delst[1]
Messages: 1157
Registered: April 2002
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Senior Member |
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Hello there,
Although I should probably know the answer to this, since all my IDL reference books have
been borrowed, hope you don't mind me asking here.
I'm a bit anal about argument checking in IDL. After establishing that the correct number
of arguments has been passed using:
n_arguments = 1
IF ( N_PARAMS() LT n_arguments ) THEN $
MESSAGE, 'Invalid number of arguments.', $
/NONAME, /NOPRINT
My standard method for checking string arguments (like filenames to read) is something
like:
IF ( N_ELEMENTS( FileNAME ) EQ 0 ) THEN BEGIN
MESSAGE, 'Input FileNAME argument not defined!', $
/NONAME, /NOPRINT
IF ( STRLEN( FileNAME ) EQ 0 ) THEN $
MESSAGE, 'Input FileNAME argument not defined!', $
/NONAME, /NOPRINT
If I pass a zero-length string, e.g. FileNAME='', the N_ELEMENTS() test passes so I always
test for a non-zero string length (it's happened). If I combine the two tests using AND,
then if the variable is undefined, the STRLEN() function generates an errors (since its
argument must be defined).
The above works great, but I have always felt that it should be unnecessary. Is there a
one-step method to test that the argument is actually defined AND that the string length
is not zero? Would the ARG_PRESENT function be useful here somehow? I read the on-line
manual, but I really don't grok the text.
Thanks for any info,
paulv
--
Paul van Delst
CIMSS @ NOAA/NCEP/EMC
Ph: (301)763-8000 x7274
Fax:(301)763-8545
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