((A, AccIn) -&gt; {B, AccOut})</tt></p>


<h3 class="typedecl"><a name="type-predicate">predicate()</a></h3>
<p><tt>predicate(Elem) = fun((Elem) -&gt; boolean())</tt></p>


<h3 class="typedecl"><a name="type-tuple_iterator">tuple_iterator()</a></h3>
<p><tt>tuple_iterator() = <a href="#type-iterator">iterator</a>(tuple())</tt></p>


<h3 class="typedecl"><a name="type-unfold">unfold()</a></h3>
<p><tt>unfold(Elem, AccIn, AccOut) = fun((AccIn) -&gt; {Elem, AccOut} | none)</tt></p>


<h3 class="typedecl"><a name