Master/texmf-dist/doc/generic/FAQ-en/html/FAQ-tabcellalign.html


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<head>
<title>UK TeX FAQ -- question label tabcellalign</title>
</head><body>
<h3>How to alter the alignment of tabular cells</h3>
<p/>One often needs to alter the alignment of a tabular <code>p</code> (&#8216;paragraph&#8217;)
cell, but problems at the end of a table row are common.  With a
<code>p</code> cell that looks like:
<blockquote>
<pre>
... & \centering blah ... \\
</pre>
</blockquote><p>
one is liable to encounter errors that complain about a &#8220;misplaced
<code>\</code><code>noalign</code>&#8221; or &#8220;<a href="FAQ-altabcr.html">extra alignment tab</a>&#8221;, or the like.
The problem is that the command <code>\\</code> means different things in
different circumstances: the <code>tabular</code> environment
switches the meaning to a value for use in the table, and
<code>\</code><code>centering</code>, <code>\</code><code>raggedright</code> and <code>\</code><code>raggedleft</code> all change the
meaning to something incompatible.  Note that the problem only
arises in the last cell of a row: since each cell is set into a box,
its settings are lost at the <code>&#38;</code> (or <code>\\</code>) that
terminates it. 
<p/>In the old days, the actual value of <code>\\</code> that the
<code>tabular</code> environment uses was only available as an
internal command.  Nowadays, the value is a public command, and you
can in principle use it explicitly:
<blockquote>
<pre>
... & \centering blah ... \tabularnewline
</pre>
</blockquote><p>
(but that&#8217;s a rather verbose way of doing things).
<p/>The <i>array</i> package provides a command <code>\</code><code>arraybackslash</code>
which restores <code>\\</code> to its correct (within table) meaning;
the command may be used in <i>array</i>&#8217;s &#8220;field format&#8221; preamble
specifications:
<blockquote>

<pre>
\begin{tabular}{... &#62;{\centering\arraybackslash}p{50mm}}
...
</pre>
</blockquote><p>
<p/>The <code>\</code><code>tabularnewline</code> and <code>\</code><code>arraybackslash</code> commands are
(somewhat) modern additions to LaTeX and the <i>array</i>
package, respectively.  In the unlikely event that neither is
available, the user may try the (old) solution which preserves the
meaning of <code>\\</code>:
<blockquote>
<pre>
\newcommand\PBS[1]{\let\temp=\\%
  #1%
  \let\\=\temp
}
</pre>
</blockquote><p>
which one uses within a table as:
<blockquote>
<pre>
... & \PBS\centering blah ... \\
</pre>
</blockquote><p>
or in the preamble as:
<blockquote>
<pre>
\begin{tabular}{...&#62;{\PBS\centering}p{5cm}}
</pre>
</blockquote><p>
<dl>
<dt><tt><i>array.sty</i></tt><dd>Distributed as part of <a href="http://www.tex.ac.uk/tex-archive/macros/latex/required/tools.zip">macros/latex/required/tools</a> (or <a href="http://www.tex.ac.uk/tex-archive/macros/latex/required/tools/">browse the directory</a>); <a href="http://www.tex.ac.uk/tex-archive/help/Catalogue/entries/array.html">catalogue entry</a>
</dl>

<p/><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=tabcellalign">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=tabcellalign</a>
</body>