[XeTeX] ifxetex package

Will Robertson wspr81 at gmail.com
Mon Jun 19 10:34:41 CEST 2006

On 6/19/06, Ross Moore <ross at ics.mq.edu.au> wrote:

>   ... clearly I've not bitten that particular bullet yet
> --- I don't like the taste of lead ...
>     ... or depleted uranium.    :-)


> If \XeTeXversion  isn't defined, so that it begets \relax
>   thereby \ifx returns \iftrue , then is there any point
> in reading further through the file ?

Ah, I see how you meant now. Maybe it would be good to add a couple of
features like this to the ifxetex package. There could be something

(At uni, therefore untested. Not sure if that \expandafter is
required, but it seemed like the right thing to do at the time to keep
things tidy even if it doesn't make a difference in execution.) An
optional argument to write a message would also be a good idea.

> This then allows an author to write documents that can
> be compiled with different processors, allowing blocks:
> \ifxetex ... \else ... \fi
> to do the correct thing according to the typesetting
> engine; e.g., employ different font-loading mechanisms.

Yes, this sort of feature is more useful for document writers.

> Surely the purpose is more for when XeTeX is *not* the engine
> --- hence it may not be e-TeX based either ---
> than for when it *is* the engine.

Yes, it's for error checking and conditionals when XeTeX ain't being used.
However, bearing that in mind I *still* think that any engine running
this package will still have eTeX extensions -- I mean, sure, it's
possible that someone will be using Knuth's TeX, but I think the
chances are fairly small.

It's a bit of a philosophical problem: what's the point in these nice
eTeX extensions if they're never used for backwards compatibility
concerns? Still, I'd be willing to change my mind since this is a
fairly extreme case.



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