s&nbsp;:&nbsp;(string&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;<span class="keywordsign">'</span>a)&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;t&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;<span class="keywordsign">'</span>a<br>
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;copy_in&nbsp;:&nbsp;?root:<span class="constructor">Dir</span>.t&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;t&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;<span class="constructor">Dir</span>.t&nbsp;<span