@Override
public Iter iter(final QueryContext ctx) throws QueryException {
final Iter iter = ctx.iter(expr);
final Item it = iter.next();
if (it == null) {
if (type.mayBeZero()) return Empty.ITER;
throw XPEMPTY.thrw(input, desc());
}
if (type.zeroOrOne()) {
if (iter.next() != null) NOTREATS.thrw(input, desc(), type);
if (!it.type.instance(type.type)) NOTREAT.thrw(input, desc(), type, it.type);
return it.iter();
}
return new Iter() {
Item i = it;
@Override
public Item next() throws QueryException {
if (i == null) return null;
if (!i.type.instance(type.type)) NOTREAT.thrw(input, desc(), type, i.type);
final Item ii = i;
i = iter.next();
return ii;
}
};
}
@Override
public Value value(final QueryContext ctx) throws QueryException {
final Value val = ctx.value(expr);
final long len = val.size();
if (len == 0) {
if (type.mayBeZero()) return val;
throw XPEMPTY.thrw(input, desc());
}
if (type.zeroOrOne()) {
if (len > 1) throw NOTREATS.thrw(input, desc(), type);
final Item it = val.itemAt(0);
if (!it.type.instance(type.type)) NOTREAT.thrw(input, desc(), type, it.type);
return it;
}
for (long i = 0; i < len; i++) {
final Item it = val.itemAt(i);
if (!it.type.instance(type.type)) NOTREAT.thrw(input, desc(), type, it.type);
}
return val;
}
/**
* Checks if the specified item is an empty sequence; if yes, throws an exception.
*
* @param it item to be checked
* @return specified item
* @throws QueryException query exception
*/
public final Item checkEmpty(final Item it) throws QueryException {
if (it == null) XPEMPTY.thrw(input, desc());
return it;
}