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Re: newbie question / concatenation of arrays of nested structure [message #17048 is a reply to message #17047]

Wed, 08 September 1999 00:00

Liam Gumley
Messages: 473
Registered: November 1994

Senior Member

Thomas Launey wrote:
> how can I concatenate 2 arrays of anonymous nested structures?
> In other word, try to concatenate the two arrays below
>
> first=replicate({a:0,b:'name',c:{d:0,e:0}},5)
> second=replicate({a:0,b:'name',c:{d:0,e:0}},3)
> third=[first,second]
> % Conflicting data structures: B,concatenation.
> % Execution halted at: $MAIN$

Since first and second are anonymous structures, IDL has no way of
knowing that they contain the same fields, e.g.

IDL> first = replicate({a:0,b:'name',c:{d:0,e:0}},5)
IDL> second = replicate({a:0,b:'name',c:{d:0,e:0}},3)
IDL> help, first, /structure
** Structure <1373ab8>, 3 tags, length=16, refs=1:
A INT 0
B STRING 'name'
C STRUCT -> <Anonymous> Array[1]
IDL> help, second, /structure
** Structure <13734c8>, 3 tags, length=16, refs=1:
A INT 0
B STRING 'name'
C STRUCT -> <Anonymous> Array[1]

You can see that the structure ids are different (1373ab8 vs. 13734c8).
IDL uses the structure id to determine if structures are equivalent.

The only way to create equivalent structures is to use named structures,
e.g.

IDL> record = {z, a:0, b:'name', c:0}
IDL> first = replicate(record, 5)
IDL> second = replicate(record, 3)
IDL> combo = [first, second]
IDL> help, first, /structure
** Structure Z, 3 tags, length=16:
A INT 0
B STRING 'name'
C INT 0
IDL> help, second, /structure
** Structure Z, 3 tags, length=16:
A INT 0
B STRING 'name'
C INT 0

Now first and second have the same structure id (z), and they can be
concatenated. Note that IDL does not like nested anonymous structures
inside a named structure, e.g.

IDL> record = {x, a:0, b:'name', c:{d:0, e:0}}
% Structures can't have anonymous structure members
% Execution halted at: $MAIN$

so you may have to re-think your original record format.

Cheers,
Liam.

--
Liam E. Gumley
Space Science and Engineering Center, UW-Madison
http://cimss.ssec.wisc.edu/~gumley

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[Message index]

		Re: newbie question / concatenation of arrays of nested structure By: davidf on Thu, 09 September 1999 00:00
		Re: newbie question / concatenation of arrays of nested structure By: colinr on Thu, 09 September 1999 00:00
		Re: newbie question / concatenation of arrays of nested structure By: Thomas A. McGlynn on Wed, 08 September 1999 00:00
		Re: newbie question / concatenation of arrays of nested structure By: Liam Gumley on Wed, 08 September 1999 00:00
		Re: newbie question / concatenation of arrays of nested structure By: Liam Gumley on Wed, 08 September 1999 00:00
		Re: newbie question / concatenation of arrays of nested structure By: davidf on Wed, 08 September 1999 00:00

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