So <code>fst</code> is a function that takes a pair of an <code>A</code> and a <code>B</code>, and yield an <code>A</code>, that’s what we expected of course!</p>
<p>And you might then guess what the type of <code>snd</code> is:</p>
<pre><code class="language-clojure">(==&gt; (pair A B)
     B)
</code></pre>
<p>From a <code>(pair A B)</code> it yield a <code>B</code>.</p>
<p>Now let’s apply the <em>PaT</em> interpretation. Because logical names are often far from computational ones, let’s replace <cod