[XeTeX] Modifying The XeTeX engine

VAFA KHALIGHI vafa.khalighi at students.mq.edu.au
Fri Dec 26 04:34:42 CET 2008

*Hi Ross**
> Oops. TeX already has  \ifcase  as a primitive.
> Are you defining it differently here, concerning upper/lowercase ?
> In that case (sic.) \iflettercase  would be a better name.

 sorry for that. I just compared the two engine's primitive commands
and I have written \ifcase by mistake. In addition to these 100
commands, there are some changes to some of the original TeX
primitives which make them suitable both
for RTL and LTR typesetting.

> But with all these new (?) names, it is important to check
> that packages are not using them already; or if any are indeed
> being used then that at least the syntax is the same so that
> files will still compile satisfactorily.

I can not guarantee this for 100 percent but TeX-e-Parsi is almost a
complete TeX system and it works with no problem with all the packages
and macros.
> The approach adopted by the pdftex developers is to keep
> the number of primitives to an absolute minimum.
> If the required effect can be obtained with macros and
> existing primitives, then this should be done rather
> than introducing new primitives.

I absolutely agree with this, But when we are talking about RTL and
LTR, XeTeX only provides four primitives \beginR,\beginL, \endR, \endL
which is honestly not enough for complex bidirectional typesetting.
There are some primitives that
can be defined in the macro level with no problem but still there are
primitives which need to be defined in the actual TeX engine and can
not be acchieved easilly in the macro level.

> My own view is less strict, in that I'd support having
> new primitives also if this has significant effects
> on the speed or efficiency of typesetting; e.g., by
> significantly reducing the amount of complicated macro
> processing.


> Please don't think that my remarks mean that I'm
> against your proposed changes --- I am not.
> Just that we should be extremely careful when
> introducing new features, and particularly careful
> in the choice of naming of new primitives.

I understand your points and in fact I appreciate your kindness and
the time that you spent to reply.

Thanks heaps
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