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Re: Is there a standard 'null' array? [message #34590 is a reply to message #34584]

Mon, 31 March 2003 08:15

JD Smith
Messages: 850
Registered: December 1999

Senior Member

On Mon, 31 Mar 2003 01:40:27 -0700, Marc wrote:

>> P.S. There was talk of adding a zero-length-array type a few years ago,
>> but the consensus was that it's probably too late to fit it easily into
>> a 25 year old program.
>
> So what? If its now introduced, old code would not have to change.
>

I think it turned out that lots of code *would* have to change. For
instance, a nice use of zero-length arrays would be as a return from
WHERE:

b=indgen(10)
b[where(b lt 0)]=5

should work without fuss, by returning a ZLA, and permitting it in
indexing operations. But what about all the code that explicitly tests
for the value "-1" returned from WHERE? The only possibility is using
tons of /ZLA keywords to turn on that feature. Ugly.

There were many other instances of this type of problem. I think a
complete re-write of IDL which explicitly does *not* preserve full
backwards-compatibility might be sensible. This IDL++ could fix this and
hundreds of other problems tied to old mistakes and conventions.
Parallel release of IDL and IDL++ for a few major versions would ease the
transition. I'm sure the sheer anticipation of people howling and
screaming is enough to stop this plan in its tracks.

JD

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[Message index]

		Re: Is there a standard 'null' array? By: JD Smith on Tue, 01 April 2003 11:55
		Re: Is there a standard 'null' array? By: James Kuyper on Tue, 01 April 2003 10:52
		Re: Is there a standard 'null' array? By: JD Smith on Tue, 01 April 2003 10:18
		Re: Is there a standard 'null' array? By: JD Smith on Tue, 01 April 2003 10:17
		Re: Is there a standard 'null' array? By: Matt Feinstein on Tue, 01 April 2003 09:20
		Re: Is there a standard 'null' array? By: JD Smith on Mon, 31 March 2003 08:15
		Re: Is there a standard 'null' array? By: marc schellens[1] on Mon, 31 March 2003 00:40
		Re: Is there a standard 'null' array? By: JD Smith on Fri, 28 March 2003 08:32

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