How can I produce vertical white space in a table with LuaLaTeX?

Question

How to add a few blank lines without using \vspace? Trying to use \\ always gets me in trouble...

Now I'm trying to format a simple lua table in LaTeX for display. I am using a combination of \\ (which requires me to use code like \noexpand\\noexpand\\) and \vspace.

The table is formated nicely EXCEPT I have to use an actual character

tex.print("-")

works fine but if I change it to

tex.print("\noexpand~")

or

tex.print(" ")

things quickly become bad.

I've also tried

tex.print("\noexpand\\hspace\noexpand{1mm\noexpand}")

but it only works if there is some initial piece of text

My Code

for i = 0, ofs + 1*idx - 1 do
    tex.print("-")
    tex.print("\noexpand\\hspace\noexpand{0.1mm\noexpand}")                            
end

Answer 1

You need to decide if you coding in TeX or you still thinking in another computer language. I can gather from your comments such as "...drives me nuts", "...things go to hell in a handbasket real quick" that you have a hard time adapting. So I would suggest rather think in "Lua", move all your coding into the Lua part.

Here is an example that justs does and calculates happy numbers that might also make you a bit happier:)

All the typesetting has been moved onto a function in this case \boxit thus having a good separation of concerns; think the same way for your table, post a minimal and maybe the community can take it up from there.

\documentclass{tufte-book}
\usepackage[listings]{tcolorbox}
\lstloadlanguages{[LaTeX]TeX, [primitive]TeX,Pascal}
\usepackage{filecontents}
\usepackage{amsmath}
\usepackage{luacode} % loads luatexbase as well
\newcommand\emphasis[2][blue]{\lstset{emph={exec,if,then,else,do,end,while,for,print,sprint,directlua,#2},
   emphstyle={\ttfamily\textcolor{#1}}}}%
\lstset{language={[LaTeX]TeX},
      escapeinside={{(*@}{@*)}}, 
       gobble=0,
       stepnumber=1,numbersep=5pt, 
       numberstyle={\footnotesize\color{gray}},%firstnumber=last,
      breaklines=true,
      framesep=5pt,
      basicstyle=\small\ttfamily,
      showstringspaces=false,
      keywordstyle=\ttfamily\textcolor{blue},
      stringstyle=\color{orange},
      commentstyle=\color{black},
      rulecolor=\color{gray!10},
      breakatwhitespace=true,
      showspaces=false,  % shows spacing symbol
      backgroundcolor=\color{gray!15}}
\begin{document}

\emphasis{return,repeat,until,function,local}
\begin{tcblisting}{}
\begin{luacode}
-- example adapted from
-- http://rosettacode.org/wiki/Happy_numbers
function boxit(color, var, s)
  return "\\fbox{\\strut\\color{violet} "..var.."} "
end
function digits(n)
  if n > 0 then return n \% 10, digits(math.floor(n/10)) end
end
function sumsq(a, ...)
  return a and a ^ 2 + sumsq(...) or 0
end
local happy = setmetatable({true, false, false, false}, {
      __index = function(self, n)
         self[n] = self[sumsq(digits(n))]
         return self[n]
      end } )
i, j = 0, 8
repeat
   i, j = happy[j] and (tex.sprint(boxit(violet, j, " ")) or i+1) or i, j + 1
until i == 17 --or j > 999
\end{luacode}
\end{tcblisting}
\end{document}