ction works well with function composition:</p><ul><li><p>The Identity Law:</p><p><code>map id x = x</code></p><p>In this context, <code>id</code> is the identity function (<a href="Bastet/Function/Category/index.html#val-id"><code>Bastet.Function.Category.id</code></a>). It's the simplest function imaginable: it just returns the value given to it. It's written like this in Ocaml:</p><pre><code class="ml"># let id x = x;;
val id : 'a -&gt; 'a = &lt;fun&gt;

# id 123;;
- : int = 123

# id &quot;foo&quot;;;
-