RE: [sv-ec] Manti 958, 974

Jonathan,

I agree that empty and uninitialized should be treated the same. 

The problem started with 19.7 saying, implicitly, that $size should also
return 'x for an empty array. I agree that is wrong.

I note that 19.7 says, "$increment shall return 1 if $left is greater
than or equal to $right and -1 if $left is less than $right." This does
not specify what happens if $left==$right. That can happen with a
1-element array, and there are such things.

I can accept $left being 0 and $right being -1 for empty arrays, but
then the definitions of $low and $high have to change, currently:

"- $low shall return the minimum of $left and $right of the dimension.
 - $high shall return the maximum of $left and $right of the dimension.
"

Regards,
Shalom

> -----Original Message-----
> From: owner-sv-ec@server.eda.org 
> [mailto:owner-sv-ec@server.eda.org] On Behalf Of Jonathan Bromley
> Sent: Tuesday, November 27, 2007 3:54 PM
> To: sv-ec@server.eda.org
> Subject: [sv-ec] Manti 958, 974
> 
> hi EC,
> 
> I've added a note to 974 proposing that it be closed as 
> duplicating (a small part of) 1447.
> 
> 958 is a little more problematic - it asks what the .size 
> method and $size() function should return when applied to 
> uninitialized dynamic arrays or queues.
> 
> My personal view is that there is little point in trying to 
> distinguish between a "null" (uninitialized) queue or dynamic 
> array and one having zero size.  If dynamic array and queue 
> variables were in fact *references* to the underlying array 
> object, I'd take a very different view.
> But they're not - at least, not from the user's viewpoint.
> The tools I've tried all seem to agree with me, and therefore 
> disagree with the current LRM.
> 
> I therefore plan to write a short proposal saying that 
> uninitialized queues and dynamic arrays have a .size() of 
> zero, and yield zero from the $size() system function.
> 
> However, that's not the end of it.  We also have the other 
> functions $left, $right, $low, $high, $increment to consider.
> At present, 19.7 says...
> 
>    When used on a dynamic array or queue dimension, 
>    these functions return information about the 
>    current state of the array. If the dimension is 
>    currently empty, these functions shall return 
>    a 'x. 
> 
> This seems very strange for $increment, which surely should 
> always return -1 for queues and dynamic arrays.
> I would also have thought that $left and $low should always 
> return 0 even if the array is empty.  The interesting 
> question is whether $right/$high should return -1 or 'x.  If 
> we agree that an empty queue or dynamic array is a legitimate 
> object, and that an uninitialized queue or dynamic array is 
> indistinguishable from an empty one, then I would have 
> thought that -1 would make more sense.
> 
> Opinions?  Please?
> --
> Jonathan Bromley, Consultant
> 
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