sp;&nbsp;pat&nbsp;:&nbsp;<span class="constructor">Ast_iterator</span>.iterator&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;<span class="constructor">Parsetree</span>.pattern&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit;<br>
&nbsp;&nbsp;&nbsp;&nbsp;payload&nbsp;:&nbsp;<span class="constructor">Ast_iterator</span>.iterator&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;<span class="constructor">Parsetree</span>.payload&nbsp;<span class="keywordsign">-&gt;</span>&nbsp;unit;<br>
&nbsp;&nbsp;&nb