[Dev-luatex] Some questions

Taco Hoekwater taco at elvenkind.com
Tue Sep 18 13:04:26 CEST 2007

Jonathan Sauer wrote:
> Hello,
> thanks for your quick reply!
>> [...]
>>> - How do I generate an error when inside Lua code? I could use
>>>   tex.write("\\errmessage{...}"), but then the error would only be
>>>   generated after the Lua code has finished executing, and after
>>>   any TeX code created previously using tex.write et.al. has
>>>   been executed.
>> - assert
>> - just print messages using texio.write_nl
>> - os.exit() also works
> The last one is a bit radical ;-)
> I was hoping to be able to say i.e. "error(message,help)" and get TeX's
> error prompt where the user can decide how to proceed.

That is not possible right now, but adding a simple interface would
be pretty straightforward.

However ... influencing the lua interpreter is not doable, so error
recovery is impossible (deleting and inserting tokens will be disabled),
and the error context will likely be useless.

Therefore, it will not be real user interaction, more a "press return
to acknowledge that you saw the error".

> But what about the other way round? What if I do not want to define
> control sequences, but access their meaning from Lua code, just as
> it is possible with registers? Is there a way?

Not now, but it is planned for the future.

Best wishes,

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