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Re: [css-syntax][selectors] Added a COLUMN token to Syntax

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Thu, 4 Apr 2013 08:30:58 -0700
Message-ID: <CAAWBYDA+dJ1NNx0wmrFwLwzp-X8M=a9AUdcxwrDv0DZzRAPEgw@mail.gmail.com>
To: Simon Sapin <simon.sapin@exyr.org>
Cc: www-style list <www-style@w3.org>
On Thu, Apr 4, 2013 at 3:13 AM, Simon Sapin <simon.sapin@exyr.org> wrote:
> Le 04/04/2013 02:06, Tab Atkins Jr. a écrit :
>> I just added a COLUMN token to the Syntax draft, matching "||".  It's
>> needed for Selectors, so it can maintain LL(1).  (Otherwise, seeing
>> "*" followed by "|" is ambiguous until you look at the *next* token.)
>
> I’m not objecting, but shouldn’t LL(1) be only an implementation concern?
> AFAICT, it is not detectable whether an implementation parses "||" as a
> single token, or looks ahead for two delim tokens.
>
> Can something undetectable make an implementation non-conforming?

Right, it's undetectable, and the LL(1) part is an implementation
concern only, but currently Selectors is LL(1), and it's nice to
maintain it.  I've already adjusted Syntax to maintain single-token
lookahead in Selectors once, with the *-match tokens.

~TJ
Received on Thursday, 4 April 2013 15:31:45 UTC

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