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<head>
<title>UK TeX FAQ -- question label alreadydef</title>
</head><body>
<h3>Package reports “command already defined”</h3>
<p/>You load a pair of packages, and the second reports that one of the
commands it defines is already present. For example, both the
<i>txfonts</i> and <i>amsmath</i> define a command <code>\</code><code>iint</code>
(and <code>\</code><code>iiint</code> and so on); so
<blockquote>
<pre>
...
\usepackage{txfonts}
\usepackage{amsmath}
</pre>
</blockquote><p>
produces a string of error messages of the form:
<blockquote>
<pre>
! LaTeX Error: Command \iint already defined.
Or name \end... illegal, see p.192 of the manual.
</pre>
</blockquote><p>
As a general rule, things that <i>amsmath</i> defines, it defines
well; however, there is a good case for using the <i>txfonts</i>
version of <code>\</code><code>iint</code> — the associated <i>tx</i> fonts have a
double integral symbol that doesn’t need to be “faked” in the way
<i>amsmath</i> does. In the case that you are loading several
symbol packages, every one of which defines the same symbol, you are
likely to experience the problem in a big way (<code>\</code><code>euro</code> is a common
victim).
<p/>There are similar cases where one package redefines another’s command,
but no error occurs because the redefining package doesn’t use
<code>\</code><code>newcommand</code>. Often, in such a case, you only notice the change
because you assume the definition given by the first package. The
<i>amsmath</i>–<i>txfonts</i> packages are just such a pair;
<i>txfonts</i> doesn’t provoke errors.
<p/>You may deal with the problem by saving and restoring the command.
Macro programmers may care to do this for themselves; for the rest of
us, there’s the package <i>savesym</i>. The sequence:
<blockquote>
<pre>
\usepackage{savesym}
\usepackage{amsmath}
\savesymbol{iint}
\usepackage{txfonts}
\restoresymbol{TXF}{iint}
</pre>
</blockquote><p>
does the job; restoring the <i>amsmath</i> version of the command,
and making the <i>txfonts</i> version of the command available as
<code>\</code><code>TXFiint</code>.
<p/>Documentation of <i>savesym</i> doesn’t amount to much: the only
commands are <code>\</code><code>savesymbol</code> and <code>\</code><code>restoresymbol</code>, as noted above.
<dl>
<dt><tt><i>amsmath.sty</i></tt><dd>Part of <a href="ftp://cam.ctan.org/tex-archive/macros/latex/required/amslatex.zip">macros/latex/required/amslatex</a> (<a href="ftp://cam.ctan.org/tex-archive/macros/latex/required/amslatex.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/macros/latex/required/amslatex/">browse</a>)
<dt><tt><i>savesym.sty</i></tt><dd><a href="ftp://cam.ctan.org/tex-archive/macros/latex/contrib/savesym/savesym.sty">macros/latex/contrib/savesym/savesym.sty</a>
<dt><tt><i>txfonts.sty</i></tt><dd>Part of <a href="ftp://cam.ctan.org/tex-archive/fonts/txfonts.zip">fonts/txfonts</a> (<a href="ftp://cam.ctan.org/tex-archive/fonts/txfonts.tar.gz">gzipped tar</a>, <a href="http://www.tex.ac.uk/tex-archive/fonts/txfonts/">browse</a>)
</dl>
<p/><p>This question on the Web: <a href="http://www.tex.ac.uk/cgi-bin/texfaq2html?label=alreadydef">http://www.tex.ac.uk/cgi-bin/texfaq2html?label=alreadydef</a>
</body>
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