// Then create a MappingIterator which applies a mapping function to each
// item in the base sequence. The mapping function is essentially the "return"
// expression, wrapped in a MappingAction object that is responsible also for
// setting the range variable at each step.
SequenceIterator base = sequence.iterate(context);
int pslot = -1;
MappingAction map = new MappingAction(context, getLocalSlotNumber(), pslot, action);
switch (actionCardinality) {
case StaticProperty.EXACTLY_ONE:
return new ItemMappingIterator(base, map, true);