[luatex] Dimensions of subboxes

[Eduardo Ochs]

Hi list,

I use LuaTeX a lot - I am even the author of
<http://angg.twu.net/dednat6/tug-slides.pdf>! - but I use very few of
the Lua functions that call the underlying TeX, so probably this is a
very basic question...

The code below runs

  \setbox0\hbox{\hbox{$a$}\hbox{$b$}\hbox{$p$}\hbox{$q$}}

and then starts a Lua REPL:

--snip--snip--
rm -Rfv /tmp/emlua/
mkdir   /tmp/emlua/
cd      /tmp/emlua/
git clone https://github.com/edrx/emlua .

rm -Rfv /tmp/emlua/tex/
mkdir   /tmp/emlua/tex/
cd      /tmp/emlua/tex/
cp -v ../edrxlib.lua .
cp -v ../Repl1.lua .

cd      /tmp/emlua/tex/
cat > a.tex <<'---'
\setbox0\hbox{\hbox{$a$}\hbox{$b$}\hbox{$p$}\hbox{$q$}}
\directlua{dofile "edrxlib.lua"}
\directlua{dofile "Repl1.lua"}
\directlua{REPL = EdrxRepl.new(); print(); REPL:repl()}
\bye
---

luatex a.tex
--snip--snip--

My question is: how do I get the dimensions of the subboxes of box0
from Lua?

  Thanks in advance!
    Eduardo Ochs
    https://github.com/edrx/emlua#introduction
    http://angg.twu.net/pict2e-lua.html