A common mistake is to forget the semicolon at the end of a definition.</li>
<li>the <code>_</code> sign represents one of the <em>primitives</em> of the language (primitives are the predefined functions of the language). It represents an <em>audio cable</em> that lets the signal pass through without transforming it. This is what one calls in mathematics the <em>identity</em> function, the signal that enters on the left comes out on the right identically. </li>
</ul>
<h3 id="example-2-adding-two-signals">Ex