t;</span>&nbsp;int&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;int&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;int
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;write_substring&nbsp;:&nbsp;<span class="constructor">Unix</span>.file_descr&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;string&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;int&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;int&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;int
&nbsp;&nbsp;<span class="keyword">val</span>&