lass="constructor">A</span></code><code class="code">&nbsp;:&nbsp;</code><code class="type"><a href="Identifiable.Thing.html">Thing</a></code><code class="code">)&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;</code><div class="sig_block"><code class="code"><span class="keyword">functor</span>&nbsp;(</code><code class="code"><span class="constructor">B</span></code><code class="code">&nbsp;:&nbsp;</code><code class="type"><a href="Identifiable.Thing.html">Thing</a></code><code class="code">)&nbsp;<span c