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Re: Array of Structures [message #38993 is a reply to message #19984]

Thu, 15 April 2004 09:38

Rick Towler
Messages: 821
Registered: August 1998

Senior Member

"Dan Steinberg" wrote in message...

> I am wondering if it is possible to create an array of structures. I
> want to read multiple different anonymous structures into a single
> variable so I can reference each structure using the variable name and
> the array index. Is this possible?

Yes, but if when you say different, you mean that their lengths are
different, you need to create an array of pointers which point to your
structures.

You can have arrays of identical structures:

IDL> x=[{a:'one',b:1},{a:'two',b:2},{a:'three',b:3}]
IDL> help, x
X STRUCT = -> <Anonymous> Array[3]
IDL> print, x[2].a
three

You can have arrays of structs that are the same length but their *initial*
tags are different:

IDL> y=[{a:'one',b:1},{c:'two',d:2},{e:'three',f:3}]
IDL> help, y[0], /struct
** Structure <15b85b0>, 2 tags, length=16, data length=14, refs=2:
A STRING 'one'
B INT 1
IDL> help, y[1], /struct
** Structure <15b85b0>, 2 tags, length=16, data length=14, refs=2:
A STRING 'two'
B INT 2
IDL> help, y[2], /struct
** Structure <15b85b0>, 2 tags, length=16, data length=14, refs=2:
A STRING 'three'
B INT 3

But you can not have an array whose elements differ in length:

IDL> y=[{a:'one',b:1},{a:'two',b:2,c:2.2},{a:'three',b:3,d:0D}]
% Conflicting data structures: <STRUCT Array[1]>,<STRUCT Array[1]>.
% Execution halted at: $MAIN$

In this case you need to create an array of pointers which point to your
structs:

z =
PTR_NEW([PTR_NEW({a:'one',b:FLTARR(3)}),PTR_NEW({a:'two',b:D BLARR(10)})])

IDL> help, *(*z)[0], /struct
** Structure <1b20198>, 2 tags, length=24, data length=24, refs=1:
A STRING 'one'
B FLOAT Array[3]
IDL> help, *(*z)[1], /struct
** Structure <1bc3420>, 2 tags, length=96, data length=92, refs=1:
A STRING 'two'
B DOUBLE Array[10]

-Rick

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[Message index]

		Array of structures. By: Nicolas Decoster on Tue, 16 May 2000 00:00
		Re: Array of structures. By: Ben Tupper on Tue, 16 May 2000 00:00
		Re: Array of structures. By: John-David T. Smith on Tue, 16 May 2000 00:00
		Re: Array of Structures By: R.Bauer on Thu, 15 April 2004 10:39
		Re: Array of Structures By: Rick Towler on Thu, 15 April 2004 09:38
		Re: Array of Structures By: Craig Markwardt on Thu, 15 April 2004 09:03
		Re: Array of Structures By: R.Bauer on Thu, 15 April 2004 08:51
		Re: Array of Structures By: K. Bowman on Thu, 15 April 2004 08:29

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