[XeTeX] Re: [MacTeX] XeTeX

[Bruno Voisin]

Le 13 avr. 04, à 15:08, Ross Moore a écrit :

> Great. That confirms it's not just my installation that has problems.
> Next try the following:
>
> \count255="4028
> \showthe\count255
> \mathcode`\(="4028
> \count255=\mathcode`\(
> \showthe\count255
> \bye
>
>
> TeX should give:
>
> [...]
>
>   whereas XeTeX gives:
>
> [...]

Same here, in both cases.

> The left-parenthesis character is at  ascii 40,
> hence at code-point 40 (decimal) in Unicode.
> Note that:
>    16424 = 40 + 2^{14}
> 67108904 = 40 + 2^{26}
>
> So it looks to me that the lower (at least 8) bits
> are correct, but not the upper ones.
>
> Using other characters (e.g. - , = and . ) give similar
> results; viz.
>   using  \mathcode`\.="013A  ( = 314 = 58 + 2^8 )
>   xetex produces:     65594  = 58 + 2^16
>
> Thus it seems that \mathcode values are either being
> read incorrectly, or are not being set correctly.
> This is something internal to the compiled binary,
> and cannot be influenced at the macro/user level.
>
> Since it's just one bit that's wrong (but not always
> the same bit!) then hopefully it's easily fixed.

I'm wondering whether it's related to encodings. The ReadMe.rtf file 
inside the .pkg installer says XeTeX works with UTF-8 and UTF-16 input 
only, and hence that the only existing TeX input files that are 
processed properly are those that use 7-bit ASCII characters 
exclusively. I don't know whether that means that all 
character-producing TeX control sequences, including math symbols, are 
converted internally to their Unicode code points, and whether that 
might explain the problem.

Bruno
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