aves as if it had been defined as follows,  
except that the iterator is not fully evaluated before elements are  
returned:</p>
 
  <pre>  filtermap(Fun, Iterator) -&gt;
      llists:foldr(fun(Elem, Acc) -&gt;
                          case Fun(Elem) of
                              false -&gt; Acc;
                              true -&gt; [Elem|Acc];
                              {true,Value} -&gt; [Value|Acc]
                          end
                   end, [], Iterator).</pre>
 
  Example:
  <pre> 