[Tex/LaTex] Is it possible to view the latex code after Lua expansion is made

luacodeluatex

When using Lua code inside Latex file, where Lua code sends to Tex Latex code to insert into the document at the location the lua code is made, it will be useful to look at the content of Latex file (internal) after the expansion is made but right before the file is compiled to pdf. This can help in debugging and in many other cases.

Is there an option to do this? A small example will help explain what I mean.

Given this latex file

\documentclass{article}
\usepackage{luacode}
\begin{document}

The following is my table

\begin{luacode}
i=6
j=8
tex.print("\\begin{tabular}{|l|l|}\\hline")
tex.print(i.."&"..j)
tex.print("\\\\ \\hline")
tex.print("\\end{tabular}")
\end{luacode}

\end{document}

Compiling this gives the pdf file:

Mathematica graphics

What I'd like to now see is the Latex file that would resulted after the Lua code expansion, which should be something as follows

\documentclass{article}
\usepackage{luacode}
\begin{document}

The following is my table

\begin{tabular}{|l|l|}\hline
6 & 8 \\\hline
\end{tabular}

\end{document}

I could not find an option to do this so far.

TL 2015

Update

Another example to make clear what is being asked here. I'd like to see not only the latex code that was generated from the lua bits of code, but the full Latex document that would result after all the expansion of all lua code in the original Latex. But this has to be done without modifying the original Latex document itself.

Assuming there is this virtual pipeline:

Latex file -> Lua code expand -> Updated Latex (internal)-> lualatex ->pdf

I'd like to get a copy of the full latex code/file just after all the lua code expanded. Here is another example. Given this Latex file input:

\documentclass{article}
\usepackage{luacode}
\begin{document}
The following is my table
\begin{luacode*}
i=6
j=8
tex.print("\\begin{tabular}{|l|l|}\\hline")
tex.print(i.."&"..j)
tex.print("\\\\ \\hline")
tex.print("\\end{tabular}")
\end{luacode*}

Our annual budget for the company is \luaexec{tex.print(200*15^3)} dollars as 
shown in this list of items
\begin{luacode*}
 tex.print("\\begin{itemize}")
 for i=1,5 do
   tex.print("\\item "..i^2)
 end
 tex.print("\\end{itemize}")
\end{luacode*}
And so on.
\end{document}

The PDF is

Mathematica graphics

I'd like to get a copy of the following latex file, which has all the Lua code expanded and gone and only the Latex code is left in its place. This file can go to a temporary file, or anywhere, as long as it is the complete Latex file as shown and not bits and pieces. This would be very useful in debugging when there is lots of Lua code in different places in the original Latex file.

\documentclass{article}
\usepackage{luacode}
\begin{document}    
The following is my table

\begin{tabular}{|l|l|}\hline
6 & 8 \\\hline
\end{tabular}

Our annual budget for the company is 675000 dollars as 
shown in this list of items

\begin{itemize}
\item 1
\item 4
\item 9
\item 16
\item 25
\end{itemize}

and so on    
\end{document}

I hope now the question is even more clear 🙂

Best Answer

The \directlua primitive is expandable so provided we formulate the code to use it directly we can show the result:

\documentclass{article}
\begin{document}

The following is my table
\showtokens\expandafter{%
  \directlua{
    i=6
    j=8
    tex.print("\noexpand\\begin{tabular}{|l|l|}\noexpand\\hline")
    tex.print(i.."&"..j)
    tex.print("\noexpand\\\noexpand\\ \noexpand\\hline")
    tex.print("\noexpand\\end{tabular}")
  }%
}
\end{document}

Note that this will not work with the luacode environment, which performs assignments in TeX and so is not expandable. This means that we have to do more work with the TeX-to-Lua step.

Based on comments, an alternative if to write the Lua code to a file would be

\documentclass{article}
\usepackage{luacode}
\begin{document}

The following is my table

\begin{luacode}
local i, j = 6, 8
local f = assert(io.open("\jobname.xxx", "w"))
local function mywrite(text)
  tex.print(text)
  f:write(text .. "\string\n")
end
mywrite("\\begin{tabular}{|l|l|}\\hline")
mywrite(i.."&"..j)
mywrite("\\\\ \\hline")
mywrite("\\end{tabular}")
\end{luacode}

\end{document}

(If used repeatedly it would be sensible to but the Lua code into a separate file, particularly the store-result code.)

Related Solutions

[Tex/LaTex] Which Lua environment should I use with LuaTeX (LuaLaTeX)

There are two questions here. You should consider asking one question at a time for your next posts.

Now to the Lua code environment. Don't use any of them if you can. Just do

\directlua{  require("myfile")  }

and put all of your Lua code in that file. See another answer for a list of directories TeX searches for the file myfile.lua.

If for some reason you can't do that (when you are only allowed to ship only one file for example) you should use the environment luacode* (with *) from the luacode package. That has the safest character catcodes. That means you can say something like:

\begin{luacode*}
texio.write_nl("This is a string with\n a newline in it")
tex.print(-2, string.format( "5 %% 4 is %d ", 5 % 4))
\end{luacode*}

(You need the -2 as the first argument to tex.sprint(), because the % sign (resulting from the double %% is interpreted from TeX as a comment sign after the environment closes. TeX sees at the end of the environment 5 % 4 is 1 and treats the % as the end of input. So you need to tell TeX that this % is a regular character. You have two choices: either pass TeX a string like this: string.format("5 \\%% 4 is ...") so that TeX sees 5 \% 4 is ... as you would do with normal text or make % a normal letter, so TeX does not recognize it as a comment sign. To do that you have to change the category code. The easiest way is to assign the special catcode table -2 to tex.print(). It is a safe catcode table, no characters have a special meaning.)

If you need to use TeX macros in Lua code, use the luacode environment (without *):

\begin{luacode}
    local current_page = tonumber(\thepage)
    texio.write_nl("We are on page " .. current_page)
\end{luacode}

And if you need to put your code in a command, use \luaexec:

\newcommand\myrepeat[2]{%
\luaexec{
  for i=1,#1 do
     tex.sprint("\luatexluaescapestring{#2}")
   end
 }}

\myrepeat{4}{Hello world}

(you can't use the environments directly in a \newcommand, but you could use \luacodestar ... \endluacodestar if you really want the environment functionality). The \luatexluaescapestring{} is necessary to escape input characters like " that would be harmful to the Lua string.

You have also asked if there is a shortcut such as the $...$ for math typesetting. No, there is none. IMO that is not such a big problem, as Lua code (in practice, but YMMV) is only used at a few points (with macros or with environments for example) and not so much in running text. Mostly in packages. (See the documentation to the luacolor package for example. Even if you don't understand the package in full detail at the first glance, you can see where the TeX code is with the \directlua calls, aliased in the example to \LuaCol@directlua and how the Lua code is separated from it in another file. See that there are only very few lines of Lua code inside the \LuaCol@directlua commands? In my opinion we can learn a lot from this code, as Heiko Oberdiek is an excellent package writer.)

Now to your second question about Saving variables. If you don't declare your variables local, they are accessible in all Lua chunks. But you are asking to pass Lua code to TeX. You can do this for example:

\begin{luacode*}
tex.sprint("\setcounter{mycounter}{" .. my_lua_value .. "}")
\end{luacode*}

to create a \setcounter command with your value. Or you can use the tex.count Lua interface:

\begin{luacode*}
tex.count[10] = my_lua_value
\end{luacode*}

and your value is in \count10. But this is a bit dangerous as you have to be certain to use a free counter.

[Tex/LaTex] Speeding up latex/lua/tikz

I imagine that the bottleneck is in running the TikZ code. However, to empirically check whether it is or not, a possible option would be to do make copies of the files that you're using and add:

function makefile(file)
   f = io.open(file,"w")
   f:write("\\documentclass{article}")
   -- you could put the rest of your preamble here, or just copy paste it later
   f:write("\\begin{document}")
end

and,

function closefile()
   f:write("\\end{document}"}
   f:close()
end

to the lua portion. Then, make wrappers:

\def\start#1{\directlua{makefile("\luatexluaescapestring{#1}")}}

\def\stop{\directlua{closefile()}}

in the tex preamble. You could then search/replace tex.print with f:write and run your file like:

\documentclass{article}
\usepackage{luacode}
\begin{luacode*} % or use a .lua file

function makefile(file)
   f = io.open(file,"w")
   f:write("\\documentclass{article}")
   f:write("\\usepackage{...}")
   f:write("\\begin{document}")
end

function closefile()
   f:write("\\end{document}"}
   f:close()
end

--your lua stuff here

\end{luacode*}

\def\start#1{\directlua{makefile("\luatexluaescapestring{#1}")}}
\def\stop{\directlua{closefile()}}

% your other preamble here

\begin{document}
\start{myfile.tex}

% your code

\stop{}
\end{document}

Some variation of the above should get you a compilable .tex file. Running it will take the lua stuff out of the equation. Thus, if it takes nearly an hour to compile you know that the bottleneck is on the TikZ side or at least get a feel for how much of the compilation time is actually taken up by running the code as opposed to producing it via lua. If it turns out that the lua is taking a significant portion of the compilation time, here are a couple of resources that might help you to speed it up:

http://www.lua.org/gems/sample.pdf

http://trac.caspring.org/wiki/LuaPerformance

and if you can confirm that TikZ takes too long, you should seriously consider the use of either TikZ's external library or the standalone package. Both can significantly speed-up the processing of documents with many tikz pictures (they are optimized for slightly different use-cases).

Best Answer

Related Solutions

[Tex/LaTex] Which Lua environment should I use with LuaTeX (LuaLaTeX)

[Tex/LaTex] Speeding up latex/lua/tikz

Related Question