[NTG-context] Snooping around in LMTX: Questions about Lua global variables

Neven Sajko nsajko at gmail.com
Tue Dec 22 18:36:51 CET 2020

Hello again,

While learning about how to drive TeX through Lua, I decided to
recursively list all Lua global variables (actually this is traversing
the _G table) in the LMTX environment, half to learn more Lua, half
for getting to know ConTeXt better.

I was quite surprised by the huge size of the environment, a file that
contains the listing of all the globals is 42 MB long! I wonder if it
would be possible to reduce the exposed globals by replacing some of
them by getter and setter-like functions? That seems like it would be
much nicer and less error prone - because Lua is so dynamic, polluting
the global namespace seems even more dangerous than in C-like
languages. I guess it could also be more performant, because Lua would
conceivably spend less time managing huge tables.

There were also some global variables with suspicious random variation
in values between runs of ConTeXt: I ran my Lua script like so
multiple times (attached, in case someone is interested in it):

    context s.lua
    rm s.tuc s.pdf s.log

And I found that the values of some variables unpredictably and randomly vary:

The variable resolvers.suffixmap.lua sometimes has the value
"scripts", and sometimes "lua". I think this means that files with the
file name suffix ".lua" are sometimes classified as general scripts
and sometimes as Lua scripts. This seems like it could even be a bug?

The variables storage.tofmodules and storage.toftables are also
interesting: they vary from run to run like this:

tofmodules: 0.175483 0.149536 0.150493 0.150005

toftables: 0.008407 0.008118 0.008395 0.008116

I'd like to know what is their purpose, if it's not to involved to explain?


More information about the ntg-context mailing list