Re: Common trouble

[davidf(at)dfanning.com (David Fanning)]

Kristian Kjaer (kristian.kjaer@risoe.dk) writes:

I should really leave this question to the common
block experts... :-)

> Q1: How do you delete a common block (other than by exiting IDL)?

You can't. Once declared, it's there forever. I hear
this may be changing in IDL 5.3. 

> Q3: Should commons be avoided altogether in IDL ?

I'll defer. Let's just say they are WAY overused in
widget programs, in my humble opinion. But there is no
question they are useful in certain--I think 
limited--situations.
 
> Q2: Why does this not work (got the same with IDL 5.1 on linux):

One of the rules of common block usage is that common
block variables cannot be arguments of procedures:

   IDL> ? common blocks

>From the error messages you are getting, I suspect the
parameters are somehow marked as a special "type" when
they come into the procedure that is different from the
type you expect them to be when you load them into common.
But this is pure speculation.

Cheers,

David

-- 
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155