Using a command to generate a table row in tabularray

Question

I have a command that generates a table row for insertion into a tblr environment as shown below:

\documentclass{book}
\usepackage{tabularray}
\begin{document}
\newcommand\MyRow[2]{
    #1 & #2 \
}
\begin{tblr}{l l}
    A & B \
    C & D \
    %\MyRow{E}{F}   % Fails here with "Misplaced alignment tab character &"
\end{tblr}
\end{document}

The command used to work with tabu but with tblr it produces an error that the alignment character & is misplaced:

Misplaced alignment tab character &.

I tried overriding the category code of & with \catcode38=12 but it didn't help. How do I generate a tblr row from a custom command?

Welcome to TeX.SE! Could you edit your code to begin with your \documentclass{} and end with \end{document} , a Minimal Working Example (MWE) please. It makes copy and pasting easier when the code can be compiled and also we do not need to guess what commands or packages you are using. — JamesT, Feb 21 '23 at 12:56

Ulrich Diez · Accepted Answer · 2023-02-21T14:09:14.993

According to section "3.2.3 Expand Macros First" of the manual of the package tabularray you need to use the key expand=\MyRow. You only get top-level-expansion of \MyRow:

\documentclass{book}
\usepackage{tabularray}
\begin{document}
\newcommand\MyRow[2]{#1 & #2 \}
\begin{tblr}[expand=\MyRow]{l l}
    A & B \
    C & D \
    \MyRow{E}{F}% Does not fail with "Misplaced alignment tab character &".
\end{tblr}
\end{document}

The question "tabularray: How to comment out some rows using \if condition inside a table stored in a macro?" and its answers provide some trickery for getting more control over expansion.

Using a command to generate a table row in tabularray

1 Answers1