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Re: Arrays of Structures [message #52446 is a reply to message #20472]

Thu, 08 February 2007 12:52

news.qwest.net
Messages: 137
Registered: September 2005

Senior Member

<mgalloy@gmail.com> wrote in message
news:1170966075.702031.236230@k78g2000cwa.googlegroups.com.. .
> On Feb 8, 12:09 pm, "R.G. Stockwell" <n...@email.please> wrote:
>> "Mick Brooks" <mick.bro...@gmail.com> wrote in message
>>
>> news:1170957886.387622.208430@l53g2000cwa.googlegroups.com.. .
...
> I'm not sure that is an expression thing either. When I try to index
> an expression, I get a syntax error:
>
> IDL> print, findgen(10)[5]
>
> print, findgen(10)[5]
> ^
> % Syntax error.

Right. This is a syntax error. IDL does not know how to parse it.
The difference is that struct.a[5] is not a syntax error, idl does know
and must know how to parse that expression. In this case though, it
is trying to access the 5th element of a, which is out of bounds.
Note that the following works

IDL> help,struct.a[0]
<Expression> INT = Array[50]

(and the rest of your post made sense to me.)

The point is, that struct is an array. If you want to acces
the array elements you must do
IDL> structs[*].a.
Or IDL lets you cast the expression into a temporary array as follows:
IDL> help, (struct.a)[22]
<Expression

IDL> help,junk.a

<Expression> INT = Array[50]

IDL> help,(junk.a)

<Expression> INT = Array[50]

> INT = 1

The original point I made is that you cannot dereference an expression, you

have to have parenthesis on it.

Cheers,
bob

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[Message index]

		Arrays of Structures By: Ben Tupper on Wed, 21 June 2000 00:00
		Re: Arrays of Structures By: news.qwest.net on Thu, 08 February 2007 12:52
		Re: Arrays of Structures By: JD Smith on Thu, 08 February 2007 12:42
		Re: Arrays of Structures By: Paul Van Delst[1] on Fri, 09 February 2007 08:01
		Re: Arrays of Structures By: Mick Brooks on Fri, 09 February 2007 02:13
		Re: Arrays of Structures By: Michael Galloy on Thu, 08 February 2007 12:21
		Re: Arrays of Structures By: news.qwest.net on Thu, 08 February 2007 11:44
		Re: Arrays of Structures By: Paul Van Delst[1] on Thu, 08 February 2007 11:32
		Re: Arrays of Structures By: Mick Brooks on Thu, 08 February 2007 11:27
		Re: Arrays of Structures By: Brian Larsen on Thu, 08 February 2007 11:11
		Re: Arrays of Structures By: news.qwest.net on Thu, 08 February 2007 11:09
		Re: Arrays of Structures By: Paul Van Delst[1] on Thu, 08 February 2007 11:02
		Re: Arrays of Structures By: Brian Larsen on Thu, 08 February 2007 10:59
		Re: Arrays of Structures By: Mick Brooks on Thu, 08 February 2007 10:04
		Re: Arrays of Structures By: Brian Larsen on Thu, 08 February 2007 09:41
		Re: Arrays of Structures By: JD Smith on Fri, 09 February 2007 12:51

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