Master/texmf-doc/doc/english/FAQ-en/html/FAQ-cmdstar.html


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<head>
<title>UK TeX FAQ -- question label cmdstar</title>
</head><body>
<h3>Commands defined with * options</h3>
<p>LaTeX commands commonly have &ldquo;versions&rdquo; defined with an asterisk
tagged onto their name: for example <code>\</code><code>newcommand</code> and
<code>\</code><code>newcommand*</code> (the former defines a <code>\</code><code>long</code> version of the
command).
<p>The simple-minded way for a user to write such a command involves use
of the <i>ifthen</i> package:
<blockquote>
<pre>
\newcommand{\mycommand}[1]{\ifthenelse{\equal{#1}{*}}%
  {\mycommandStar}%
  {\mycommandNoStar{#1}}%
}
\newcommand{\mycommandStar}{starred version}
\newcommand{\mycommandNoStar}[1]{normal version}
</pre>
</blockquote><p>

This does the trick, for sufficiently simple commands, but it has
various tiresome failure modes, and it requires <code>\</code><code>mycommandnostar</code>
to take an argument.
<p>Of course, the LaTeX kernel has something slicker than this:
<blockquote>
<pre>
\newcommand{\mycommand}{\@ifstar
                     \mycommandStar%
                     \mycommandNoStar%
}
\newcommand{\mycommandStar}[2]{starred version}
\newcommand{\mycommandNoStar}[1]{normal version}
</pre>

</blockquote><p>
(Note that arguments to <code>\</code><code>mycommandStar</code> and <code>\</code><code>mycommandNoStar</code>
are independent &mdash; either can have their own arguments, unconstrained
by the technique we&rsquo;re using, unlike the trick described above.)
The <code>\</code><code>@ifstar</code> trick is all very well, is fast and efficient, but
it requires the definition to be 
<a href="FAQ-atsigns.html"><code>\</code><code>makeatletter</code> protected</a>.
<p>A pleasing alternative is the <i>suffix</i> package.  This elegant
piece of code allows you to define variants of your commands:

<blockquote>
<pre>
\newcommand\mycommand{normal version}
\WithSuffix\newcommand\mycommand*{starred version}
</pre>
</blockquote><p>
The package needs <a href="FAQ-etex.html">e-LaTeX</a>, but any new enough
distribution defines LaTeX as e-LaTeX by default.  Command
arguments may be specified in the normal way, in both command
definitions (after the &ldquo;<code>*</code>&rdquo; in the <code>\</code><code>WithSuffix</code>
version).  You can also use the TeX primitive commands, creating a
definition like:
<blockquote>
<pre>
\WithSuffix\gdef\mycommand*{starred version}
</pre>
</blockquote><p>
<dl>
<dt><tt><i>ifthen.sty</i></tt><dd>Part of the LaTeX distribution
<dt><tt><i>suffix.sty</i></tt><dd>Distributed as part of <a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/bigfoot.zip">macros/latex/contrib/bigfoot</a> (<a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/bigfoot.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/macros/latex/contrib/bigfoot/">browse</a>)
</dl>
<p>
<p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=cmdstar">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=cmdstar</a>
</body>