[luatex] Luatex primitive names

[Manuel Pégourié-Gonnard]

Hans Hagen a écrit :
>>> Third (and this is why the above two functions are needed) starting
>>> with version 0.40, luatex in --ini mode will contain only the tex82
>>> primitives and \directlua, no extra primitives *at all*.
>>
>>   We'd have kind of a boostrap problem if \directlua wasn't included ;-)
> 
> that's why only that one is there (and not even \luatexversion)
> 
Btw, extra care should be taken while writing code that should be portable:
- across different version of LuaTeX
- across different TeX engines.

Before this, as a macro writer, my preferred way of detecting the underlying
engine would probably have been testing whether \luatexversion is defined. Now
I'd rather test for \directlua. *But* if some day Jonathan include Lua as a
scripting language in XeTeX, things will be more complicated.

Also, if I want to test for the LuaTeX version in order to know whether I should
use \directlua0 or \directlua, it is a bit complicated. I guess there is a
solution (no time to find it and write down the code right now) but anyway my
point is:

I think the LuaTeX manual should state clearly a recommended way of detecting
LuaTeX (and its version) so that macro writers can (hopefully) use it and no
other way that could become wrong in the future.

Manuel.