Counters for multiline row/cells

[wwojciech]

It seems that standard counters do not work as expected in multiline setup, i.e. this code

\begin{tblr}{hlines, vlines}
    \SetCell[r=2]{c} {\arabic{rownum}} & A \\ & B \\
    \SetCell[r=2]{c} {\arabic{rownum}} & C \\ & D
\end{tblr}

gives:

while I would rather expect:

As a workaround, I can use \UseTblrLibrary{counter}, however, the counter is then not reset across different tables (I would probably need to reset it every time, before a new table?).

Eventually, I could use the construct like below, but it does not work:

\begin{tblr}{hlines, vlines}
    \SetCell[r=2]{c} {\arabic{rownum}} & A \\ & B \\
    \SetCell[r=2]{c} {\arabic{rownum+1}} & C \\ & D
\end{tblr}

[muzimuzhi]

Sounds like a request for "real row/column number" counters.

\AddToHook{env/<envname>/begin}{<code>} can be used to add code to the \begin{<envname>} of an environment. It's documented in texdoc lthooks-doc.

BTW you can use \inteval{\value{rownum}+1} to do integer calculations.

\inteval is added to the kernel since LaTeX2e 2022-06-01, see texdoc ltnews, issue 35. \inteval{<int expr>} is let to \int_eval:n expl3 function and the latter is a thin wrapper around \the\intexpr <int expr>\relax, thus the supported syntax is limited, see texdoc etex and this TeX-SX answer.

[wwojciech]

So, I see that \inteval{\value{rownum}/2}rounds the result up, i.e. for instance for rownum=3 it returns 2. Do you know if there is any explicit way or ceiling?

[muzimuzhi]

If you meant floor (round towards negative infinity), \inteval{(\value{rownum}-1)/2} does the trick.

More powerful thus slower \fpeval{floor(\value(rownum), 0)} gives the same result. floor floating-point math function is documented in texdoc interface3, sec. 29.12.3 "Operations".

[wwojciech]

Thanks, I meant ceiling (the smallest integer not less than a given number, or rounding towards positive infinity, if you prefer).
Actually \inteval{\value{rownum}/2} gives expected results, i.e. 1, 2, ... for "real" row numbers. However, I think, syntacticly, it would be better to use \fpeval{ceil(\value{rownum}/2)}.

[muzimuzhi]

I filed a feature request, see

• Real or visual row/column counters #486.

[wwojciech]

Thanks lot for your valuable response and for the feature request!