devdocs/elisp/simple-macro.html


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 <h3 class="section">A Simple Example of a Macro</h3> <p>Suppose we would like to define a Lisp construct to increment a variable value, much like the <code>++</code> operator in C. We would like to write <code>(inc x)</code> and have the effect of <code>(setq x (1+ x))</code>. Here’s a macro definition that does the job: </p>  <div class="example"> <pre class="example">(defmacro inc (var)
   (list 'setq var (list '1+ var)))
</pre>
</div> <p>When this is called with <code>(inc x)</code>, the argument <var>var</var> is the symbol <code>x</code>—<em>not</em> the <em>value</em> of <code>x</code>, as it would be in a function. The body of the macro uses this to construct the expansion, which is <code>(setq x (1+ x))</code>. Once the macro definition returns this expansion, Lisp proceeds to evaluate it, thus incrementing <code>x</code>. </p> <dl> <dt id="macrop">Function: <strong>macrop</strong> <em>object</em>
</dt> <dd><p>This predicate tests whether its argument is a macro, and returns <code>t</code> if so, <code>nil</code> otherwise. </p></dd>
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    <a href="https://www.gnu.org/software/emacs/manual/html_node/elisp/Simple-Macro.html" class="_attribution-link">https://www.gnu.org/software/emacs/manual/html_node/elisp/Simple-Macro.html</a>
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