| Re: STRUCT_ASSIGN [message #12620] |
Sun, 23 August 1998 00:00  |
Martin Schultz
Messages: 515
Registered: August 1997
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Senior Member |
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Robert S. Mallozzi wrote:
>
> Hi all,
>
> I have a structure defined as follows:
>
> a = { f1: 0, f2: { x: 0, y: 0}}
>
> [...]
> So, must I resort to field-by-field copy? The problem
> is that "a" is actually an object ("self"), which has
> some member variables that are large structures.
> A field-by-field copy would be tedious, as each
> structure has on the order of 30 fields, or so.
> I wanted to write a generic "set" method that will
> initialize the object's structures with some data.
> If I must do a field-by-field copy, I would then
> have to have several "set" methods, each of which is
> specialized for each of the different stuctures
> within the object.
>
As Mark points out, the problem here is that you are actually using two
different anonymous structures. There has been a recent discussion in
this newsgroup about a similar problem: If you type help,a.f2,data,/stru
you will se something like :
** Structure <10304508>, 2 tags, length=4, refs=2:
X INT 0
Y INT 0
** Structure <10304708>, 2 tags, length=4, refs=1:
X INT 10
Y INT 20
The number in <> identifies the structure "type"...
> So, must I resort to field-by-field copy? The problem
> is that "a" is actually an object ("self"), which has
> some member variables that are large structures.
> A field-by-field copy would be tedious, as each
> structure has on the order of 30 fields, or so.
> I wanted to write a generic "set" method that will
> initialize the object's structures with some data.
> If I must do a field-by-field copy, I would then
> have to have several "set" methods, each of which is
> specialized for each of the different stuctures
> within the object.
>
What you describe here sounds like a typical application for pointers.
Nesting structures within structures within structures ... can usually
only be achieved with the help of these things. Here is an example:
a = { f1:0, f2:ptr_new() }
data = { x:10, y:20 }
a.f2 = ptr_new(data,/NO_COPY) ; careful: no_copy means
; "data" will be lost afterwards!
help,*a.f2,/stru
You can test the contents of your sub-structure with tag_names():
print,tag_names(*a.f2)
Hope, this gives a hint in the right direction,
Martin.
--
------------------------------------------------------------ -------
Dr. Martin Schultz
Department for Earth&Planetary Sciences, Harvard University
109 Pierce Hall, 29 Oxford St., Cambridge, MA-02138, USA
phone: (617)-496-8318
fax : (617)-495-4551
e-mail: mgs@io.harvard.edu
Internet-homepage: http://www-as.harvard.edu/people/staff/mgs/
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