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Re: [css-style-attr] SVG WG comments on CSS Styling Attributes Level 1

From: Bjoern Hoehrmann <derhoermi@gmx.net>
Date: Wed, 08 Sep 2010 03:39:38 +0200
To: Håkon Wium Lie <howcome@opera.com>
Cc: www-style@w3.org, www-svg@w3.org
Message-ID: <mumd86dbec1u53hll8gfnk8ipcma5ju7hh@hive.bjoern.hoehrmann.de>
* Håkon Wium Lie wrote:
>Introducing e-notation in CSS would have a considerable cost. We would
>need to change the CSS core grammar, which is -- sort of -- our
>constitution. Constitutions can be changed, but only for truly
>important things, when there is long-standing consensus.

The CSS Working Group changes the core syntax on average anually, and
allowing this notation would not require changes to the core syntax:

  <number> [eE] - <integer> <unit>?

is tokenized as DIMENSION,

  <number> [eE] + <integer>

is tokenized as DIMENSION DELIM NUMBER, and

  <number> [eE] + <integer> <unit>

is tokenized as DIMENSION DELIM DIMENSION (and all these sequences
are allowed in the relevant places). It may be beneficial to change
the core rules (giving scientific numbers and scientific dimensions
their own tokens so comments between the tokens are disallowed and
to disallow non-integer exponents) and there would be a difference
between SVG and CSS in that CSS would likely allow the "e" and the
unit identifier to be escaped, but these are all familiar issues.

Having scientific notation in CSS or SVG is not really useful, the
numbers where some may consider them beneficial will typically be
beyond specification or implementation limits or be unstable, e.g.
due to accumulated rounding errors; SVG Tiny 1.2 for instance has
the bounds -32,767.9999 to +32,767.9999 (with at most that many
digits). It's at best useful for content that won't work very well.
Björn Höhrmann · mailto:bjoern@hoehrmann.de · http://bjoern.hoehrmann.de
Am Badedeich 7 · Telefon: +49(0)160/4415681 · http://www.bjoernsworld.de
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Received on Wednesday, 8 September 2010 01:40:16 UTC

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