W3C home > Mailing lists > Public > www-style@w3.org > August 2011

RE: [CSS3 Values] referencing width or height explicitly

From: Brian Manthos <brianman@microsoft.com>
Date: Fri, 19 Aug 2011 22:14:14 +0000
To: Tab Atkins Jr. <jackalmage@gmail.com>
CC: "www-style@w3.org" <www-style@w3.org>
Message-ID: <9710FCC2E88860489239BE0308AC5D171260A9@TK5EX14MBXC264.redmond.corp.microsoft.com>
Most properties don't do something useful when you map them to infinity.  That's why I picked 0.  But yah, whatever value the committee comes up with is fine.  I'm just saying "don't kill the expression format, kill the edge case".

-----Original Message-----
From: Tab Atkins Jr. [mailto:jackalmage@gmail.com] 
Sent: Friday, August 19, 2011 2:50 PM
To: Brian Manthos
Cc: www-style@w3.org
Subject: Re: [CSS3 Values] referencing width or height explicitly

On Fri, Aug 19, 2011 at 1:54 PM, Brian Manthos <brianman@microsoft.com> wrote:
> That seems like the tail wagging the dog to me.

I agree; I was just explaining the reason it was that way.


> When the "calc(5px / (10px - 10%) )" resolves to "calc(5px / 0)", mapping that to a known value (like 0) seems reasonable.

That doesn't seem sensical.  Surely it should map to infinity px?


> Let's take another example...
> div {
> width: calc(
> 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002px / 0.000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001);
> }
>
> Should "really precise" applications treat this as valid at parse time with a resolved value of "2px" and "not so precise" applications treat this at parse time as invalid?

Yes, that's generally true.  Even if there wasn't a prohibition
against division by 0, less precise applications would see it as
0px/0, which does not give "2px" as an answer.  (It doesn't even have
a reasonable-but-invalid answer like "infinity px" - 0/0 is
straight-up indeterminate.)

~TJ

Received on Friday, 19 August 2011 22:14:42 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 17:20:43 GMT