Problem with hhline with tables having more than 9 columns

Question

I found out that the hhline does not print lines when the argument is greater than 9 as in \hhline{|*14{-}|}. It works well when doing instead \hhline{|*9{-}*5{-}|} as the following file shows:

\documentclass{article}

\usepackage{hhline}
\usepackage{colortbl}

\begin{document}

\begin{center}
\small\sf
\begin{tabular}{|c|c|c|c|c|c|c|c|c|} \hhline{|*9{-}|}
\rowcolor[gray]{.8} & & \multicolumn{7}{c|}{Year} \\ \hhline{|*9{-}|}
a & a & a & a & a & a & a & a & a \\ \hhline{|*9{-}|}
\end{tabular} 
\end{center}

\begin{center}
\small\sf
\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|c|c|c|} \hhline{|*9{-}*5{-}|}
\rowcolor[gray]{.8} & & \multicolumn{12}{c|}{Year} \\ \hhline{|*9{-}*5{-}|}
a & a & a & a & a & a & a & a & a & a & a & a & a & a \\ \hhline{|*9{-}*5{-}|}
\end{tabular} 
\end{center}

\begin{center}
\small\sf
\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|c|c|c|} \hhline{|*14{-}|}
\rowcolor[gray]{.8} & & \multicolumn{12}{c|}{Year} \\ \hhline{|*14{-}|}
a & a & a & a & a & a & a & a & a & a & a & a & a & a \\ \hhline{|*14{-}|}
\end{tabular} 
\end{center}

\end{document}

Is this the expected behavior ?

Answer 1

The expected thing is to put the number in {...} as in \hhline{|*{14}{-}|}. If you do only \hhline{|*14{-}|}, LaTeX actually thinks that you want to replicate 1 time the string 4, and not 14 times the string -.

The fact that it works correctly on one-digit numbers is a bit misfortunate since people then think it's the correct syntax; but it is not.

As a side note, please do not use \sf, use \sffamily instead. Reasons are explained in the question: Does it matter if I use \textit or \it, \bfseries or \bf, etc.