>Parsetree</span>.value_description&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit;<br>
&nbsp;&nbsp;&nbsp;&nbsp;with_constraint&nbsp;:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="constructor">Ast_iterator</span>.iterator&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;<span class="constructor">Parsetree</span>.with_constraint&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit;<br>
&nbsp;&nbsp;}<br>
&nbsp;&nbsp;<span class="keyword">val</span>&nbsp;default_iterator&nbsp;:&nbsp;<span class