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Re: getting structure elements by tag name string [message #33487]

Wed, 08 January 2003 09:41

R.Bauer
Messages: 1424
Registered: November 1998

Senior Member

s@visita2.die.upm.es wrote:
> Hi all,
>
> I try to use a structure as a bad substitute for a hash map (hashs or
> associative lists or dictionaries or anything similar don't exist in
> IDL, do they?)
>
> Suppose I have a structure like this:
> s = {a:7,b:9}
>
> and I have a variable that contains a tag name:
> tag = 'a'
>
> Now I want to put the value of the structures element with name tag into a
> new variable called value:
> value = s.tag
>
> This doesn't work of course, because tag is undefined for this structure.
> But how can I get this the elements value?

I often use followings:

walue=s.(0)

for example is symbolic the firs tag of s.

You can extend this a bit more with a function of our library

value=s.(tag_position(s,'a'))

http://www.fz-juelich.de/icg/icg-i/idl_icglib/idl_source/idl _html/dbase/download/tag_position.tar.gz

or as idl5.5 binary

http://www.fz-juelich.de/icg/icg-i/idl_icglib/idl_source/idl _html/dbase/download/tag_position.sav

>
> I found a somewhat crude way:
> res = execute('value =' + 's.' + tag)
>
> That works, but it's really ugly. Is there a better way to do this?
>
> And, is there a way to delete an element from a structure?

Yes,

therefore we use delete_tag
http://www.fz-juelich.de/icg/icg-i/idl_icglib/idl_source/idl _html/dbase/download/delete_tag.tar.gz
http://www.fz-juelich.de/icg/icg-i/idl_icglib/idl_source/idl _html/dbase/download/delete_tag.sav

and just for interest you can add or replace or rename tags on each of
the structure levels.

For further routines and licensing please have a look at

http://www.fz-juelich.de/icg/icg-i/idl_icglib/idl_lib_intro. html

best regards

Reimar
--
Reimar Bauer

Institut fuer Stratosphaerische Chemie (ICG-I)
Forschungszentrum Juelich
email: R.Bauer@fz-juelich.de
------------------------------------------------------------ -------
a IDL library at ForschungsZentrum Juelich
http://www.fz-juelich.de/icg/icg-i/idl_icglib/idl_lib_intro. html
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[Message index]

		Re: getting structure elements by tag name string By: R.Bauer on Wed, 08 January 2003 09:41
		Re: getting structure elements by tag name string By: JD Smith on Wed, 08 January 2003 08:09
		Re: getting structure elements by tag name string By: David Fanning on Wed, 08 January 2003 05:40
		Re: getting structure elements by tag name string By: Karsten Rodenacker on Wed, 08 January 2003 05:04
		Re: getting structure elements by tag name string By: Karsten Rodenacker on Wed, 08 January 2003 05:01
		Re: getting structure elements by tag name string By: Pavel A. Romashkin on Thu, 09 January 2003 09:20

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