">t</a></span> <span>&#45;&gt;</span> </span><span><span>(<span class="type-var">'b</span>, <span class="type-var">'x</span>)</span> <a href="index.html#type-t">t</a></span></code></dt><dd><p>Apply a function across everything of type <code>'a</code> in a parameterised type <code>'a t</code>.</p></dd></dl></details></div></div></div><dl><dt class="spec value" id="val-(&lt;@&gt;)"><a href="#val-(&lt;@&gt;)" class="anchor"></a><code><span class="keyword">val</span> (&lt;@&gt;) : <span class="arg"><span>(<spa