an>&nbsp;<span class="constructor">Parsetree</span>.constructor_declaration&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit;<br>
&nbsp;&nbsp;&nbsp;&nbsp;expr&nbsp;:&nbsp;<span class="constructor">Ast_iterator</span>.iterator&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;<span class="constructor">Parsetree</span>.expression&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit;<br>
&nbsp;&nbsp;&nbsp;&nbsp;extension&nbsp;:&nbsp;<span class="constructor">Ast_iterator</span>.iterator&nbsp;<span class="