Re: Usage of System Variables

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

Liam Gumley (Liam.Gumley@ssec.wisc.edu) writes:

> A colleague and I were having a discussion recently about system
> variables in IDL. My colleague regularly uses system variables such as
> !p.region, !p.font, !p.margin for configuring plots. My opinion is that
> system variables should be used as little as possible. In fact the only
> system variable I ever modify is !p.multi for creating multiple plots.
> Otherwise I prefer to use keywords to plot, surface, tv, tvscl, etc.
> 
> It seems to me that modifying global system variables is not a good
> idea, since they have a global effect. These days you can write
> applications which run while leaving the IDL command line active, and
> setting/modifying system variables in this case sounds like a recipe for
> disaster.

Hear! Hear!
 
> Can anyone think of other cases where setting a system variable is the
> only way to achieve the desired effect (e.g. !p.multi)?

!Mouse.Button = 0 
While !Mouse.Button NE 4 DO BEGIN

Well, unless you are writing widget programs, which you should
be. :-)

Cheers,

David
-- 
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
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