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Re: Negative indexing and the WHERE function in IDL 8.0 [message #72166 is a reply to message #72165]

Thu, 19 August 2010 05:09

svhhaugan
Messages: 8
Registered: August 2010

Junior Member

On Aug 18, 6:31 pm, Chris Torrence <gorth...@gmail.com> wrote:
> Hi all,
>
> A possible solution is to use the new /NULL keyword to WHERE:

[..]

> Hope this helps.

Not really. First of all, it isn't IDL 7-compatible. Second,
that change by itself only prevents against accidental modification
of your data immediately after the WHERE. Program logic will
continue past that point based on a false assumption.

How about using "compile_opt strictarrsubs" (which is IDL 7-
compatible)
to imply what it always implied in IDL 7 and before: all negative
array subscripts are illegal, whether scalar or arrays.

If only you'd gone with the option that "new semantics go with a new
program suffix" (as I recommended when I was asked). As it is now,
your customers may find and use stuff from "out there", and it will
not work the way it does on IDL 7 when executed by IDL 8. That's
wasting a lot of people's time. Take e.g. SolarSoft, almost 50 000
routines that are potentially broken in IDL 8 but not in IDL 7,
due to this new feature. And no automatic way to fix it. Inserting
a compile_opt statement can easily be done automatically. This
will certainly break a few of them, I'm sure, but at least it'll
cause a *crash* when something's wrong. Not squash the error
message and let the code go on doing something that was
never foreseen.

Stein

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[Message index]

		Re: Negative indexing and the WHERE function in IDL 8.0 By: wlandsman on Thu, 19 August 2010 06:29
		Re: Negative indexing and the WHERE function in IDL 8.0 By: svhhaugan on Thu, 19 August 2010 05:09
		Re: Negative indexing and the WHERE function in IDL 8.0 By: chris_torrence@NOSPAM on Wed, 18 August 2010 09:31
		Re: Negative indexing and the WHERE function in IDL 8.0 By: svhhaugan on Fri, 20 August 2010 03:36
		Re: Negative indexing and the WHERE function in IDL 8.0 By: Greg Hennessy on Thu, 19 August 2010 18:35
		Re: Negative indexing and the WHERE function in IDL 8.0 By: penteado on Thu, 19 August 2010 11:02

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