[colortbl] "breaks" '\hdotsfor' command

[vp1981]

Hello,
I noticed that colortbl "breaks" '\hdotsfor' command from amsmath package. Please consider the following two examples.

First example without package 'colortbl':

\documentclass{article}

\usepackage{amsmath}

\begin{document}

This is an example borrowed from the amsmath package documentation:
\begin{equation}
  \begin{pmatrix}
    D_1t&-a_{12}t_2&\dots&-a_{1n}t_n\\
    -a_{21}t_1&D_2t&\dots&-a_{2n}t_n\\
    \hdotsfor[2]{4}\\
    -a_{n1}t_1&-a_{n2}t_2&\dots&D_nt
  \end{pmatrix}
\end{equation}

\end{document}

Second example, with package 'colortbl'

\documentclass{article}

\usepackage{colortbl}
\usepackage{amsmath}

\begin{document}

This is an example borrowed from the amsmath package documentation:
\begin{equation}
  \begin{pmatrix}
    D_1t&-a_{12}t_2&\dots&-a_{1n}t_n\\
    -a_{21}t_1&D_2t&\dots&-a_{2n}t_n\\
    \hdotsfor[2]{4}\\
    -a_{n1}t_1&-a_{n2}t_2&\dots&D_nt
  \end{pmatrix}
\end{equation}

\end{document}

The second example shows that '\hdotsfor' command works differently when the 'colortbl' package is used.

[davidcarlisle]

Hmm yes, colortbl does document that any commands that add stretchable glue to an array cell need adjusting, however I agree it isn't obvious that colortbl is being used here (it modifies the underlying array/tabular implementation so affects all arrays even if they do not use colour) I'll see what I can do

[davidcarlisle]

colortbl already had some AtBeginDocument clauses fixing up specific package incompatibilities, I think that here something like this should work, I have added it to the test document but would be added to colortbl.sty in a real fix ``` \documentclass{article} \usepackage{colortbl} \makeatletter \AtBeginDocument{% \ifx\hdots@for\@undefined\else \def\hdots@for#1#2{\multicolumn{#2}c% {\m@th\[email protected]\mkern-#1\dotsspace@ \hskip\stretch{-.5}% \xleaders\hbox{$\m@th\mkern#1\dotsspace@.\mkern#1\dotsspace@$}% \hfill \hskip\stretch{-.5}% \mkern-#1\dotsspace@}% }% \fi } \makeatother \usepackage{amsmath} \begin{document} This is an example borrowed from the amsmath package documentation: \begin{equation} \begin{pmatrix} D_1t&-a_{12}t_2&\dots&-a_{1n}t_n\\ -a_{21}t_1&D_2t&\dots&-a_{2n}t_n\\ \hdotsfor[2]{4}\\ -a_{n1}t_1&-a_{n2}t_2&\dots&D_nt \end{pmatrix} \end{equation} \end{document} ```

[vp1981]

Thank you,
that '\AtBeginDocument' magic works fine.