Tabularray: Macros & counters inside table

expansiontabularray

Working with the tabularray package, I'm trying to use a macro that operates a counter inside a table, like so:

\documentclass{article}

\usepackage{tabularray}

\begin{document}

\newcounter{dbg}

\newcommand{\ctr}{\refstepcounter{dbg}\arabic{dbg}}

\ctr
\ctr
\ctr

\begin{tabular}{ccc}
    \ctr & \ctr & \ctr \\
    \ctr & \ctr & \ctr \\
\end{tabular}

\begin{tblr}{ccc}
    \ctr & \ctr & \ctr \\
    \ctr & \ctr & \ctr \\
\end{tblr}

\end{document}

The \ctr macro works fine outside of tables and in a regular tabular, but inside tabularray, the results are… surprisingly large.

It looks like tabularray is expanding the macro multiple times internally.

The \NewTableCommand mechanism isn't allowed to produce cell text, so it doesn't seem to help me. There's the (somewhat limited) expand option, but I haven't seen it have any effect on this, and neither did I find a way to sneak in a \protect or \noexpand to make it work.
Splitting the counting and printing into two commands, a \NewTableCommand-defined one that steps the counter and a regular one to print it almost works, but all the stepping is done before the table is set, so all cells show the final value of the counter.

Is there some way to get tabularray to expand my cells as intended?

Best Answer

The package evaluates the body multiple times for trial typesetting there is an issue in its github about that. Code was added to allow preserving counters based on the mechanism tabularx uses to preserve counters

https://github.com/lvjr/tabularray/discussions/83 and linked issues

As shown there, in recent releases you can use

\UseTblrLibrary{counter}

which loads code that fixes this (by storing and restoring counter values).

Related Solutions

[Tex/LaTex] Completely expandable loop macro that also works in tabular

There are a number of possible approaches to doing this without the complexity: I'll cover a couple using expl3. First, if you don't mind keeping things non-expandable then you could do something like

\documentclass{article}
\usepackage{expl3}
\ExplSyntaxOn
\cs_new_protected:Npn \For #1#2#3#4
  {
    \int_step_inline:nnnn {#1} {#2} {#3 - 1} {#4}
  }
\cs_new_eq:NN \fpeval \fp_eval:n
\ExplSyntaxOff
\newcommand*\N{5}
\begin{document}

\begin{tabular}{|r|*{\N}{r|}}
    \hline
    $x$:   \For{0}{1}{\N}{&#1}\\
    \hline
    $e^x$: \For{0}{1}{\N}{& \fpeval{round(exp(#1),5)}}\\
    \hline
\end{tabular}
\end{document}

where the code to implement the cells can then be given at point-of-use. You could instead have a two-part setup where the functions are pre-coded: this is then expandable at point-of-use

\documentclass{article}
\usepackage{expl3}
\ExplSyntaxOn
\cs_new_protected:Npn \For #1#2#3#4
  {
    \int_step_function:nnnN {#1} {#2} {#3 - 1} #4
  }
\cs_new_eq:NN \fpeval \fp_eval:n
\ExplSyntaxOff
\newcommand*\N{5}
\newcommand\CellNumber[1]{&#1}
\newcommand\CellExp[1]{&\fpeval{round(exp(#1),5)}}
\begin{document}
\begin{tabular}{|r|*{\N}{r|}}
    \hline
    $x$:   \For{0}{1}{\N}\CellNumber\\
    \hline
    $e^x$: \For{0}{1}{\N}\CellExp\\
    \hline
\end{tabular}
\end{document}

In both cases, the \int_step_... functions work much like David's answer: the loop itself is done by expansion. You can't do an assignment to \x or similar and have expandability.

An alternative approach if you are using LuaTeX is to do everything in Lua: the primitive here is expandable so you can use a perhaps more familiar approach (the question suggests a C background).

\documentclass{article}
\newcommand\For[4]{%
  \directlua{%
    for x = #1, (#3 - 1), #2 do
      tex.print(#4)
    end
  }%
}
\newcommand*\N{5}
\makeatletter
\let\Percent\@percentchar
\makeatother
\begin{document}

\begin{tabular}{|r|*{\N}{r|}}
    \hline
    $x$:   \For{0}{1}{\N}{"&" .. x}\\
    \hline
    $e^x$: \For{0}{1}{\N}{"&" .. string.format("\Percent.3f", math.exp(x))}\\
    \hline
\end{tabular}
\end{document}

For the number formatting, we need % which is a bit awkward in TeX: I've given a 'user' name to the LaTeX kernel command \@percentchar (a % which isn't a comment char).

Tabularray: Expand multiple macros

Here is a different answer than my other, which requires minimal changes from the OP's MWE. Basically, instead of employing \newcommand to define his intro and outro, use \newtoks. That way, one can use [expand=\the] to get both of them expanded inside of tblr:

\documentclass{article}

\usepackage{tabularray}

\newtoks\introrow
\newtoks\outrorow

\introrow{Cat & Dog \\}
\outrorow{Frog & Duck \\}

\begin{document}

\begin{tblr}[expand=\the]{cc}
    \the\introrow
    Crow & Hawk \\
    \the\outrorow
\end{tblr}

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Completely expandable loop macro that also works in tabular

Tabularray: Expand multiple macros

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