public XmlQueryType AncestorsOf(XmlQueryType source, XmlQueryType filter) {
Debug.Assert(filter.IsNode && filter.Count == 1 && filter.IsSingleton);
List<XmlQueryType> list = new List<XmlQueryType>();
XmlQueryCardinality card = XmlQueryCardinality.None;
foreach (XmlQueryType sourceItem in source) {
switch (sourceItem.TypeCode) {
case XmlTypeCode.Node:
case XmlTypeCode.ProcessingInstruction:
case XmlTypeCode.Comment:
case XmlTypeCode.Text:
case XmlTypeCode.Element:
case XmlTypeCode.Namespace:
case XmlTypeCode.Attribute:
if (schemaSet == null) {
card |= (AddFilteredPrime(list, UntypedDocument, filter) * XmlQueryCardinality.ZeroOrOne)
+ (AddFilteredPrime(list, UntypedElement, filter) * XmlQueryCardinality.ZeroOrMore);
}
else {
card |= (AddFilteredPrime(list, Document, filter) * XmlQueryCardinality.ZeroOrOne)
+ (AddFilteredPrime(list, Element, filter) * XmlQueryCardinality.ZeroOrMore);
}
break;
case XmlTypeCode.Document:
card |= XmlQueryCardinality.Zero;
break;
default:
Debug.Assert(sourceItem.IsAtomicValue, "missed case for a node");
break;
}
}
// Make sure that cardinality is at least Zero
return PrimeProduct(ChoiceType.Create(list), source.Cardinality * card);
}