"mdzsyn-comment"># -&gt; 10</span></code></pre><p>Janet has many macros provided for you (and you can write your own).  Macros are
just functions that take your source code and transform it into some other
source code, usually automating some repetitive pattern for you.
</p>
<h2 id="Optional-arguments">Optional arguments
</h2>
<p>Most Janet functions will raise an error at runtime if not passed exactly the
right number of arguments.  Sometimes, you want to define a function with
optional arguments, where th