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<span id="Defining-Macros"></span><div class="header">
<p>
Next: <a href="Invoking-Macros.html" accesskey="n" rel="next">Invoking Macros</a>, Up: <a href="Defining-New-Texinfo-Commands.html" accesskey="u" rel="up">Defining New Texinfo Commands</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Command-and-Variable-Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="Defining-Macros-1"></span><h3 class="section">17.1 Defining Macros</h3>
<span id="index-Defining-macros"></span>
<span id="index-Macro-definitions_002c-Texinfo"></span>
<span id="index-macro"></span>
<p>You use the Texinfo <code>@macro</code> command to define a macro, like this:
</p>
<div class="example">
<pre class="example">@macro <var>macroname</var>{<var>param1</var>, <var>param2</var>, …}
<var>text</var> … \<var>param1</var>\ …
@end macro
</pre></div>
<p>The <em>parameters</em> <var>param1</var>, <var>param2</var>, … correspond to
arguments supplied when the macro is subsequently used in the document
(described in the next section).
</p>
<span id="index-Macro-names_002c-valid-characters-in"></span>
<span id="index-Names-of-macros_002c-valid-characters-of"></span>
<p>For a macro to work consistently with TeX, <var>macroname</var> must
consist entirely of letters: no digits, hyphens, underscores, or other
special characters. So, we recommend using only letters. However,
<code>makeinfo</code> will accept anything consisting of alphanumerics,
and (except as the first character) ‘<samp>-</samp>’. The ‘<samp>_</samp>’ character
is excluded so that macros can be called inside <code>@math</code> without
a following space (see <a href="Inserting-Math.html">Inserting Math</a>).
</p>
<p>If a macro needs no parameters, you can define it either with an empty
list (‘<samp>@macro foo {}</samp>’) or with no braces at all (‘<samp>@macro
foo</samp>’).
</p>
<span id="index-Body-of-a-macro"></span>
<p>The definition or <em>body</em> of the macro can contain most Texinfo
commands, including macro invocations. However, a macro definition
that defines another macro does not work in TeX due to limitations
in the design of <code>@macro</code>.
</p>
<span id="index-Parameters-to-macros"></span>
<p>In the macro body, instances of a parameter name surrounded by
backslashes, as in ‘<samp>\<var>param1</var>\</samp>’ in the example above, are
replaced by the corresponding argument from the macro invocation. You
can use parameter names any number of times in the body, including zero.
</p>
<span id="index-Backslash-in-macros"></span>
<p>To get a single ‘<samp>\</samp>’ in the macro expansion, use ‘<samp>\\</samp>’. Any
other use of ‘<samp>\</samp>’ in the body yields a warning.
</p>
<span id="index-Spaces-in-macros"></span>
<span id="index-Whitespace-in-macros"></span>
<p>The newline characters after the <code>@macro</code> line and before the
<code>@end macro</code> line are ignored, that is, not included in the
macro body. All other whitespace is treated according to the usual
Texinfo rules.
</p>
<span id="index-Recursive-macro-invocations"></span>
<span id="index-rmacro"></span>
<p>To allow a macro to be used recursively, that is, in an argument to a
call to itself, you must define it with ‘<samp>@rmacro</samp>’, like this:
</p>
<div class="example">
<pre class="example">@rmacro rmac {arg}
a\arg\b
@end rmacro
…
@rmac{1@rmac{text}2}
</pre></div>
<p>This produces the output ‘a1atextb2b’. With ‘<samp>@macro</samp>’ instead of
‘<samp>@rmacro</samp>’, an error message is given.
</p>
<span id="index-unmacro"></span>
<span id="index-Macros_002c-undefining"></span>
<span id="index-Undefining-macros"></span>
<p>You can undefine a macro <var>foo</var> with <code>@unmacro <var>foo</var></code>.
It is not an error to undefine a macro that is already undefined.
For example:
</p>
<div class="example">
<pre class="example">@unmacro foo
</pre></div>
<hr>
<div class="header">
<p>
Next: <a href="Invoking-Macros.html" accesskey="n" rel="next">Invoking Macros</a>, Up: <a href="Defining-New-Texinfo-Commands.html" accesskey="u" rel="up">Defining New Texinfo Commands</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Command-and-Variable-Index.html" title="Index" rel="index">Index</a>]</p>
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