Re: David: for your book ?

[Craig Markwardt <craigmnet(at)cow.physics.wisc.edu>]

Martin Schultz <martin.schultz@dkrz.de> writes:
> As an aside, I recently found another problem in terms of backward
> compability (I am 
> sure something similar was already mentioned in this newsgroup, but this
> was the first
> time I had this problem):
>    I tried to write a routine that takes advantage of the new StrMatch
> and StRegex
> functions in 5.3. In order to ensure backward compatibility, I enclosed
> these function calls
> with
>     IF !Version.Release GE 5.3 THEN BEGIN
>     ENDIF
> 
> However, a colleague tells me: no chance! The program will report a
> syntax error when run in 
> IDL 5.2! So, the problem is that IDL looks for a function of this name
> during compile stage
> and doesn't care if it will ever be used.
...

There is a way to do this without defining an external function, by
using FORWARD_FUNCTION properly:

FORWARD_FUNCTION stregex, strmatch
IF !Version.Release GE 5.3 THEN BEGIN
   foo = stregex(bar)
   sm = strmatch(eg)
ENDIF

This will make sure that IDL will always recognize strmatch & stregex
as functions during the compilation stage, and there will be no syntax
errors in any IDL version.  It is harmless in IDL 5.3.  If you really
want the warning message, then by all means go ahead and make your own
strmatch definitions et al.

Have fun,
Craig

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Craig B. Markwardt, Ph.D.         EMAIL:    craigmnet@cow.physics.wisc.edu
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