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Re: [css-values] [css-color] XSL-FO and CSS - expression languages compared

From: Liam R. E. Quin <liam@w3.org>
Date: Mon, 05 Dec 2016 20:03:02 -0500
Message-ID: <1480986182.29052.480.camel@w3.org>
To: "Tab Atkins Jr." <jackalmage@gmail.com>, Florian Rivoal <florian@rivoal.net>
Cc: www-style list <www-style@w3.org>
On Mon, 2016-12-05 at 15:48 -0800, Tab Atkins Jr. wrote:
On Wed, Nov 16, 2016 at 9:05 PM, Florian Rivoal <florian@rivoal.net>
> wrote:
> > It's been a while since I last though seriously about that, but I
> > seem to remember that
> > as long as we had something which was continuous, piece-wise
> > linear, and strictly monotonic, we were good,
> > and that breaking any of the three could mean complications.
> > 
> > mod is piecewise linear, but not continuous or monotonic
> > abs is piecewise linear and continuous, but not monotonic
> > floor, ceiling, min and max are piecewise linear and continuous,
> > and monotonic but not strictly monotonic
> > round is piecewise linear but not continuous, and monotonic but not
> > strictly monotonic
> > 
> > I may be misremembering the criteria, and they may not all be of
> > equal difficulty, though. I seem to remember this discussion being
> > raised by dbaron, so maybe he remembers better.
> I think you got it right. Point is that it needs to be invertible to
> be usable in several spots in CSS, which those criteria satisfy.

Invertible in the sense of f¯¹ ? Is that true of calc()? in general no
because you could multiply by zero in an expression.

sin(), cos(), sqrt() are probaby OK if defined over a percentage of a
circle, but not tan().

But is the inverse function what's actually needed, or just a
dependency graph?

Received on Tuesday, 6 December 2016 01:03:15 UTC

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