[XeTeX] ifxetex package

[Will Robertson]

On 19/06/2006, at 2:00 , Bruno Voisin wrote:

> Did you look at all the checks made by ifpdf.sty and ifvtex.sty, to
> make sure the package is loaded only once even if called several
> times by other packages, and to make sure the \ifpdf and \ifvtex
> switches return the correct value whatever version of pdfTeX and VTeX
> is running? In XeTeX, in particular, that would mean \ifxetex
> returning a correct value even when called on a version of XeTeX in
> which \XeTeXversion had not been introduced.
>
> Do you think it would be worth wandering into the same level of
> complexity for XeTeX?

Hi Bruno,

LaTeX itself ensures than a package is only loaded once, and for  
Plain I've only added enough smarts that you at least shouldn't get  
error messages.

Why would there be a version of XeTeX *without* the primitive  
\XeTeXversion?

\ifpdf and \ifvtex are provided by their respective packages -- no  
point me copying their functionality.

After uploading this package, I felt a bit silly. I don't think this  
needs to be in a package by itself. It's easy enough to say
   \ifdefined\XeTeXversion...\fi

So maybe I'll end up removing it from CTAN...on the other hand maybe  
there is something that will pop up to be useful to include in there.

Will