ues of a type are equal, and the <code>ORD</code> interface to define whether two values are <i>greater-than</i>, <i>less-than</i> or <i>equal</i>.</p><h4 id="rings"><a href="#rings" class="anchor"></a>Rings</h4><p>Types that you can both <code>add</code> and <code>multiply</code> are <a href="Bastet/Interface/module-type-SEMIRING/index.html"><code>Bastet.Interface.SEMIRING</code></a>s. If you include <code>subtract</code> you get a <a href="Bastet/Interface/module-type-RING/index.html"><code>Bastet.Interfa