if (_unbounds == null || i == _unbounds.size())
return exp.evaluate(group, ctx, params);
// grab the extent for this variable
UnboundVariable var = (UnboundVariable) _unbounds.get(i);
Extent extent = ctx.getBroker().newExtent(var.getType(), true);
Iterator itr = extent.iterator();
try {
// if the extent was empty, then alias the variable to null
if (!itr.hasNext()) {
var.setValue(null);
return matches(exp, group, ctx, params, i + 1);