&nbsp;<span class="keyword">val</span>&nbsp;mem&nbsp;:&nbsp;(<span class="keywordsign">'</span>a,&nbsp;<span class="keywordsign">'</span>b)&nbsp;<span class="constructor">Hashtbl</span>.t&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;<span class="keywordsign">'</span>a&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;bool<br>
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;remove&nbsp;:&nbsp;(<span class="keywordsign">'</span>a,&nbsp;<span class="keywordsign">'</span>b)&nbsp;<span class="constructor">H