hor"></a><code><span class="keyword">val</span> last_exn : <span><span class="type-var">'a</span> <a href="index.html#type-t">t</a></span> <span>&#45;&gt;</span> <span class="type-var">'a</span></code></dt><dt class="spec value" id="val-is_prefix"><a href="#val-is_prefix" class="anchor"></a><code><span class="keyword">val</span> is_prefix : <span><span class="type-var">'a</span> <a href="index.html#type-t">t</a></span> <span>&#45;&gt;</span> <span>prefix:<span><span class="type-var">'a</span> <a href="index