Re: () eq () vs () = ()

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Subject: Re: () eq () vs () = ()
From: "G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>
Date: Fri, 30 Sep 2011 07:02:44 -0400

At 2011-09-30 11:48 +0100, Andrew Welch wrote:

On 30 September 2011 10:54, Stefan Krause <stf@xxxxxxxx> wrote: > To make the confusion complete, deep-equals((),()) returns true(), which is IMHO the most expected behavior.

heh so

() = () returns false

deep-equals((),()) returns true
That's interesting, I'm guessing it has to be a 'just because'
reason... unless its because, ahem, deep down everything is equal  :)

:{)}

Fwiw, it applies to the other comparison operators too, eg () > ()
returns false, () ge () returns ().

Ummmmm ... if either operand of *any* symbol comparison is the empty set the result returned is false() because the result is initialized to false() before determining any of the individual comparisons. It then finds there are none, so there is nothing to do.

And XPath 2 3.5.1(2) dictates very similarly that if either operand is the empty sequence the result returned is the empty sequence without doing any other work. And if you convert the empty sequence to a Boolean you end up with false() as well.

And the very first bullet of Functions 15.3.1 for deep-equal() reads "If the two sequences are both empty, the function returns true."

Does all that qualify as "just because"? At least it is well defined. As a user I like the fact that such behaviours are well-defined ... I'm sure developers must appreciate that as well.

I'm trying to understand where your frustration with the specification or the behaviours lies.

Thanks!

. . . . . . . . . Ken

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Current Thread

Re: () eq () vs () = (), (continued)
- Stefan Krause - 30 Sep 2011 09:54:26 -0000
  - Andrew Welch - 30 Sep 2011 10:48:17 -0000
    - David Carlisle - 30 Sep 2011 11:00:49 -0000
    - Wendell Piez - 30 Sep 2011 15:16:08 -0000
    - Message not available
    - G. Ken Holman - 30 Sep 2011 11:03:12 -0000 <=
    - Andrew Welch - 30 Sep 2011 11:28:30 -0000
    - Message not available
    - G. Ken Holman - 30 Sep 2011 12:26:43 -0000
    - Andrew Welch - 30 Sep 2011 12:44:53 -0000
    - David Carlisle - 30 Sep 2011 12:58:14 -0000

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Re: () eq () vs () = (), Wendell Piez	Thread	Re: () eq () vs () = (), Andrew Welch
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