# Re: RTL directionality in LaTeX

From: Peter Krautzberger <peter.krautzberger@mathjax.org>
Date: Tue, 5 Nov 2013 13:02:17 -0800
Message-ID: <CABqxo83K74MhC2k7CpESH91wQ7+EcYAUtMaB2SBsy0oa8WS3TQ@mail.gmail.com>
To: Ross Moore <ross.moore@mq.edu.au>
Cc: Murray Sargent <murrays@exchange.microsoft.com>, Frédéric WANG <fred.wang@free.fr>, Khaled Hosny <khaledhosny@eglug.org>, "www-math@w3.org" <www-math@w3.org>, Azzeddine LAZREK <a_lazrek@yahoo.fr>
Ross wrote:

> Using  \dir  is bad, as it leads to a macro-name clash with the Xy-pic
package,

That's good to know.

> Please always discuss such syntax proposals with the LaTeX math experts
before making anything public.

I believe I am to "blame" here. I thought this mailing list was fitting
since it combines TeX and web experts (and has very little noise). I might
turn out to be wrong but so far it seems to be productive.

Peter.

On Tue, Nov 5, 2013 at 12:34 PM, Ross Moore <ross.moore@mq.edu.au> wrote:

> Hi all,
>
> On 06/11/2013, at 6:55 AM, Murray Sargent wrote:
>
> > See also the Unicode Arabic Mathematical Alphabetic Symbols<
> http://www.unicode.org/charts/PDF/U1EE00.pdf>, which were standardized
> after the Arabic math reference below was published. A Unicode-enabled
> LaTeX could represent these symbols directly as Unicode characters.
> Alternatively, they can be represented as styles. The Unicode
> representation has the advantage that it can be transmitted using plain
> text.
> >
> > Murray
>
> > But if it is just some pseudo-LaTeX syntax, I don't think the actual
> notation matters much, but \rtl{} looks more LaTeX-like to me.
> > Or perhaps \dir[rtl]{...} with an optional parameter so that someone can
> still switch back to LTR with \dir[ltr]{...}.
>
> I beg to disagree.
> Choosing a syntax that already conflicts with other usages of the
> macro name causes massive headaches for both developers and users.
>
> Directionality is a property of the math environment, not of the
> content in that environment, so this form is inappropriate:
>
>    \macro[property]{content} .
>
> Rather it should be
>
>   \begin{<environment>}<property-spec>
>     ... content ...
>   \end{<environment>}
> e.g.
>    $$\mathdir{rtl} x^2$$
> or
>    $$[rtl] x^2$$
>
> Using  \dir  is bad, as it leads to a macro-name clash with the Xy-pic
> package, used extensively over the past 15+ years for mathematical
> and Computer Science (and other) diagrams.
> It is a staple for Category Theorists.
>
> I would vote for inserting something like \mathdir{rtl}
> at the beginning of the environment.
> This allows for:
>  1. an easy definition for backward compatibility
>       — let \mathdir just gobble its argument and do nothing;
>  2. a view forward to a hacky implementation
>       — the environment macro can look-ahead 1 token, to check
>       whether it is \mathdir and act accordingly.
>
> A proper implementation would be to have the directionality
> passed as an optional argument, with default set according to
> what is commonly used in the language of the surrounding text.
> John Plaice just gave a great talk on this kind of "mixing
> directionalities" problem, 2 weeks ago at TUG 2013 — held in Japan,
> where such issues are an everyday occurrence.
>
> Anything else creates new syntax which current developers will
> then need to find a way to handle. (La)TeX math is already very
> complicated, and any such new concepts are not easily accommodated.
>
>
> Please always discuss such syntax proposals with the LaTeX math
> experts before making anything public. (As you are doing here.)
> It is all too easy to try something that looks simple --- at least
> for the user --- but is actually fraught with hidden pitfalls.
>
> (They did this with WebEQ in the early years of MathML, introducing
> incompatibilities for  {table}  environments. Thank goodness this
> never really caught on.)
>
>
> >
> > --
> > Frédéric Wang
> > maths-informatique-jeux.com/blog/frederic<
> http://maths-informatique-jeux.com/blog/frederic>
>
>
> Hope this helps,
>
>         Ross
>
> ------------------------------------------------------------------------
> Ross Moore                                       ross.moore@mq.edu.au
> Mathematics Department                           office: E7A-206
> Macquarie University                             tel: +61 (0)2 9850 8955
> Sydney, Australia  2109                          fax: +61 (0)2 9850 8114
> ------------------------------------------------------------------------
>
>
>
>
>

Received on Tuesday, 5 November 2013 21:02:44 UTC

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