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Re: [css-values] Concrete proposal for unit algebra in calc()

From: Liam R E Quin <liam@w3.org>
Date: Wed, 23 Apr 2014 20:32:48 -0400
Message-ID: <1398299568.31293.27.camel@slave.barefootcomputing.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: Zack Weinberg <zackw@panix.com>, www-style list <www-style@w3.org>
On Wed, 2014-04-23 at 16:56 -0700, Tab Atkins Jr. wrote:

> * We'll allow unit powers other than 1/0/-1.
> * We'll drop the rule that makes parse-time-detectable zero-division
> invalid; instead, it'll trigger this infinity handling as well.

This was done for XSL-FO years ago - the most recent text is at:
http://www.w3.org/TR/2012/WD-xslfo20-20120117/#d2e7915

The document refers normatively (in section 5.11.5) to IEEE 754 and
explicitly includes positive and negative infinity, positive and
negative zero (sign) and NaN (not-a-number).

5.12 (lower in the same document) has the core functions we included,
although we already knew we needed to extend it before 2.0 went much
further - e.g. adding sin(), sqrt() etc; we'd agreed at one point to
allow the functions (and operators) in XPath 2 Functions and operators.

A minor advantage to using the same functions where possible is that
they've already been implemented, and also that at least one
implementation of XSl-FO also does CSS-based formatting. But I'm not
going to push harder than this.

Liam

-- 
Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://fromoldbooks.org/
Ankh: irc.sorcery.net irc.gnome.org freenode/#xml
Received on Thursday, 24 April 2014 00:32:59 UTC

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