[texhax] [lltx] issue with unicode-math, spanish and LuaLaTeX

[Philipp Stephani]

Am 12.07.2011 16:39, schrieb Taco Hoekwater:
> On 07/12/2011 04:33 PM, Taco Hoekwater wrote:
>> On 07/12/2011 04:22 PM, Ulrike Fischer wrote:
>>>
>>> With xetex I can at least use
>>>
>>> \XeTeXmathcharnumdef\test=\XeTeXmathcodenum`\x
>>>
>>> but none of the various combination of \Umathchardef + \Umathcode
>>> etc seems to work in luatex.
>>
>> NYI, see:
>
> Actually, that does not mean I think it is a good idea. The
> conceptual problem is that \XeTeXmathcodenum (and therefore
> also \Umathcodenum) can return a signed int to represent an
> unsigned value, with is pretty horrible.

Yes, and the bit-packed structure of the mathcodenum isn't quite elegant 
either. The Lua table representation is fine, but unfortunately there is 
no way to represent that in TeX.

>
> Why is it so important to be able to do a mathcharnumdef
> (instead of a macro definition or straight \Umathchardef?)

Because of the pattern that Ulrike mentioned:

\Umathcodenum `a = \Umathcodenum `b
\Umathcharnumdef \foo = \Umathcodenum `b

The second pattern is used to save a math code and restore it later. You 
could save the math code in an integer register or macro, but then you 
couldn't use that as a mathematical character shorthand.
I don't know what reasons Knuth had to introduce special syntax for 
\chardefs/\mathchardefs, but I think most TeX users expect this syntax 
to be present.