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RE: [CSS3-mediaqueries]: Invalid test cases in test suite

From: Arron Eicholz <Arron.Eicholz@microsoft.com>
Date: Thu, 29 Sep 2011 16:22:23 +0000
To: Boris Zbarsky <bzbarsky@MIT.EDU>, "public-css-testsuite@w3.org" <public-css-testsuite@w3.org>
Message-ID: <07349ECFC3608F48BC3B10459913E70B148E3D22@TK5EX14MBXC293.redmond.corp.microsoft.com>
On Wednesday, September 28, 2011 1:24 PM Boris Zbarsky wrote:
> On 9/28/11 4:13 PM, Arron Eicholz wrote:
> > CSS 2.1 still doesn't cover 0 exactly. What is 0?
> 
> The CSS 2.1 spec says its numbers are real numbers.

But what is a real number to CSS? There is no reference from the CSS spec to go off of for real numbers. Again I am asking for reference or us being explicit about 0 and +0. Maybe we need to do both.

You are correct that we say real numbers but the spec doesn't say if 0 is included in positive or negative numbers (for example when we discuss property values that take positive numbers).

> 
> Typical fairly equivalent definitions of 0 would then include:
> 
> * The smallest element of the subset of the real numbers called the
>    "Natura numbers".
> * The additive identity in the field structure of the real numbers.
> * "That thing defined in the first Peano axiom."
> 

You are just reinforcing my point. This definition basically says that 0 is a real number and most likely would be a positive number. I personally don't think it should be, but again we need to say that in the spec.

> 
> > Since -0 is equivalent to 0 and is not a negative number that completely
> explains -0. It does not however explicitly explain what 0 or +0 is or isn't. We
> must therefore draw the conclusion that +0 is positive and 0 can be both
> positive and negative.
> 
> I have no idea what you're talking about here.

I am talking about the problem that 0 and +0 are not explicitly stating that they are or are not positive numbers. We are explicit about -0 why not also be explicit about +0 and 0?

> 
> > We need explicit text explaining this
> 
> How much more explicit than "these are real numbers" can you get?  Or do
> you want the CSS spec to include some subset of the field axioms for the
> reals, enough to prove that +0 == 0 == -0 (using the usual definitions of unary
> + and - for the reals, which would likewise need to be included in the CSS
> spec)?
> 
> We can explicitly say that -0 == 0 == +0, of course, as an informative note or
> something, if you think that makes things clearer for people who are
> unfamiliar with the term "real number"....
> 

I am not disagreeing with you on the basis that I don't understand what you are saying. What I am saying that the spec needs to be more explicit or have more references. We seem to be lacking both at this time. Personally I think we just need to be more explicit and add the following text:
 
-0 is equivalent to 0 and is not a negative number. +0 is equivalent to 0 and is not a positive number. 0 is neither positive nor negative number.

That text solves my problem and I think solves Tab's as well.

--
Thanks,
Arron Eicholz



Received on Thursday, 29 September 2011 16:23:02 GMT

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