sp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;find_opt&nbsp;:&nbsp;elt&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;t&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;elt&nbsp;option<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;find_first&nbsp;:&nbsp;(elt&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;bool)&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;t&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;elt<br>
&nbsp;&nbsp;&nbsp;&nbsp;&