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Re: [mediaqueries] @media not (unsupported-media-feature) v.s. @media not (unsupported + syntax)

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Wed, 22 Apr 2015 12:32:23 -0700
Message-ID: <CAAWBYDCxiw_7t4o4SpguiDfkbWyndm_P6za0gOjSw=1i1EtjWw@mail.gmail.com>
To: Simon Sapin <simon.sapin@exyr.org>
Cc: Florian Rivoal <florian@rivoal.net>, www-style list <www-style@w3.org>
On Wed, Apr 22, 2015 at 9:45 AM, Simon Sapin <simon.sapin@exyr.org> wrote:
> Another option that came up in today’s call is tri-state logic:
>
> Intermediate terms of a media query, in addition to evaluating to either
> true or false, could evaluate to "maybe" with the following rules:
>
> * <general-enclosed> evaluates to maybe
> * `not maybe` evaluates to maybe
> * `maybe and X` evaluates to maybe
> * `maybe or X` evaluates to X
> * <media-query> evaluating to maybe is the same as evaluating to false.
>
> The point of all this is that for Y that evaluates to true and Z that has
> evaluates to true, me might want `Y and Z` to evaluate to true.

You got that last part confused.  What we want is for "Y or Z" to be
true if Y or Z is true, regardless of what the other one is.  In
particular, we don't want a <general-enclosed> on one side to mess
that up, because it's irrelevant.

Your truth table is mostly correct, but I think "maybe AND false"
should be false.  In particular, we should be implementing the Kleene
3-value logic: http://en.wikipedia.org/wiki/Three-valued_logic#Kleene_and_Priest_logics

~TJ
Received on Wednesday, 22 April 2015 19:33:10 UTC

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