Most Common IDL Programming Errors

Folks,

I realize you don't much like to play games (I'm thinking
back to the "Yo mama's so ..." thread), but you have no 
idea how hard it is to come up with new topics for my IDL 
Tips page every week. (Especially so because I try to 
understand what I write and make available, which
pretty much rules out 4/5 of what I read on this newsgroup.)

Anyway, I was sitting here wondering why we don't have any
beer in the house again, and it occurred to me that I should
have a page listing the 10 or 15 most common IDL programming
errors with their solutions. But I can only think of three.

Here are the three errors I most commonly see in IDL programs. 

1. IDL programs are named incorrectly. The last program 
   module in the file should have the same name as the file.
   Utility modules in the file should start with the name
   of the "command" (or last) module to make clear their
   purpose.

2. KEYWORD_SET is used to check whether a keyword is
   "used" or "defined". This function should only be
   used with binary keywords. (I plan to avoid all
   nuance with this list, and just go with black and 
   white pronouncements.)

3. People draw graphics willy-nilly in widget programs
   without having the faintest idea which window their
   graphics might show up in.

What would be on your list? Of course, typos are assumed. :-)

Cheers,

David
-- 
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Se****e ma de ni thui. ("Perhaps thou speakest truth.")