="type-var">'b</span> <a href="argument-1-F/index.html#type-t">F.t</a></span></code></dt><dt class="spec value" id="val-(&lt;$)"><a href="#val-(&lt;$)" class="anchor"></a><code><span class="keyword">val</span> (&lt;$) : <span class="type-var">'a</span> <span>&#45;&gt;</span> <span><span class="type-var">'b</span> <a href="argument-1-F/index.html#type-t">F.t</a></span> <span>&#45;&gt;</span> <span><span class="type-var">'a</span> <a href="argument-1-F/index.html#type-t">F.t</a></span></code></dt><dt class="s