key, 'id) cmparable</code> is a module of functions, here it only includes <code class="code">cmp</code>.
<p>

    Unlike normal functions, when created, it comes with a unique identity (guaranteed
    by the type system).
<p>

    It can be created using function <a href="Belt_Id.html#VALcomparableU"><code class="code">Belt_Id.comparableU</code></a> or<a href="Belt_Id.html#VALcomparable"><code class="code">Belt_Id.comparable</code></a>.
<p>

    The idea of a unique identity when created is that it makes s