| Scope_VarFetch Bug or Feature? [message #47508] |
Tue, 14 February 2006 13:46 |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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Folks,
Here is a short test program and main-level program:
;*****************************************************
PRO test
names = Scope_Varname(Level=1,Count=varcount)
FOR j=0,varcount-1 DO BEGIN
Print, 'Fetching variable ' + names[j] + '...'
mainvar = Scope_VarFetch(names[j], Level=1, /Enter)
Help, mainvar
ENDFOR
END
a = 5
b = c
test
END
;*****************************************************
Compile and run the main-level program. Yes, it will
cause an error. Don't worry about it. :-)
When the error occurs, you will have two variables at
the main level (LEVEL=1 in SCOPE_ parlance), a and b.
The variable a is equal to 5 and b is undefined.
Now, just type "test" and the test program runs.
It will find both variables at the main level.
But, as far as I can tell there is no way to learn
anything more about the variables unless I retrieve
them. BUT, I can't retrieve an undefined variable.
It causes an error. :-(
(According to the documentation the ENTER keyword should
cause a variable with the name I am trying to fetch (b, in
this case) to be created at the main-level, but this
doesn't seem to work either. At least I still get the error.
This DOES seem like a bug to me.)
This is all causing me some heartburn, because I need to
retrieve variables at a particular level and save them.
All works well unless I try to retrieve undefined variables,
and in this particular application, I cannot assume there
won't be undefined variables.
Does this seem like a bug to you, or a feature? Is the
only alternative to CATCH the error?
Cheers,
David
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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