e-clojure">(==&gt; T1 T2 T3) ≡ (==&gt; T1
                      (==&gt; T2 T3))

(==&gt; T1 T2 T3 T4) ≡ (==&gt; T1
                         (==&gt; T2
                              (==&gt; T4 T4)))

;; etc...
</code></pre>
<ul>
<li>an occurrence of a <strong>variable</strong> <code>x</code>, <code>y</code>, <code>A</code>, <code>B</code>, etc.</li>
</ul>
<p>The variables are for example introduced by the abstractions (they can also be introduced by parameteric definitions, as discussed later on). The ty