On Fri, Sep 25, 2015 at 4:09 PM, Orion Poplawski <orion@cora.nwra.com> wrote:

I'm just starting to take a look how luatex makes use of lua. And it appears that luatex does not merely use lua, but extends it in various ways, essentially creating new lua dialect. Is the assessment correct? Is there any documentation on this?

hm, the only relevant patch I can see here

https://www.tug.org/svn/texlive/trunk/Build/source/libs/lua52/lua-5.2.4-PATCHES

is about utf-8 chars in names.

For the rest, there are a bunch of libraries as lpeg that are embedded in the interpreter.

The current manual is luatexref-t.pdf at

foundry.supelec.fr/scm/viewvc.php/trunk/manual/luatexref-t.pdf?root=luatex&view=log

Also, is luajit used in the same way, or would it be possible to use a system installed luajit in building luatex?

Theoretically yes, but I dont know if the patches are still ok in this case.

While we try to use the stock lua/luajit as much as possibile,

the builder can decide to patch the source to match the TeXLive build requirements,

and the luatex team can decide to modify the source to match the development requirements.

Also we try to keep luajit as drop-in replacement of lua so that minimize the effort of adapting a format.

Given the current status of luajit, the rule is not to depend on luajittex --- this means that the same task in luajittex should be done

in luatex; usually luajittex is faster than luatex with jit off, but in some situations there is no gain, and it's better to use luatex then.

luigi