| Re: Global variables and IDL [message #15014 is a reply to message #11537] |
Tue, 13 April 1999 00:00   |
roberson
Messages: 5
Registered: May 1998
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Junior Member |
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In article <19990412230259.15932.00002313@ng117.aol.com>,
Russ051990 <russ051990@aol.com> wrote:
:I'm certain that IDL has a global variable (I remember it being mentioned in
:Fanning's book), but don't remember how to invoke it. Maybe someone else can
:provide that for you.
Use a common block. That requires adding only one extra statement to each
routine that uses an element of the common, and requires no other code
changes.
:In the meantime, you could use a "FORTRAN-like" structure to hold your "global"
:variables, and pass just the pointer to the structure around if you'd like.
:The structure can be declared like this
:common = PTR_NEW ({ varname1:value1, varname2:value2, ..., varnamen:valuen})
You would have to carry the pointer around everywhere (the pointer name
will not be global in scope even though the heap values pointed to are
global); and you would have to make many code changes to dereference.
Fortunately those changes could be made in batch mode with any good
editor.
The online help shows, in Widget Example 2, another method.
When you are using a widget and you ask for the value of the 'top' field
of the event structure, you get the user value associated with the top
level widget of the widget you are processing the event for. If that
user value has been set to a widget ID, you can use WIDGET_CONTROL
routines to extract values from that widget, or to set values in that widget.
But if you're going to do that and you don't need the graphical part to
change, you might as well make the user value a PTR. [Not a structure,
though, as it is a copy of the value that is put into the widget unless
you use /NO_COPY.]
In any case, this discussion is inappropriate for comp.lang.idl
(which is about the Interface Definition Language). I have cross-posted
to the appropriate newsgroup. comp.lang.idl-pvwave, and set followups
to go to there.
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