static A nuLike lowestConceptByField(Class c, S field) {
ret lowestConceptByField(db_mainConcepts(), c, field);
}
static A lowestConceptByField(Concepts concepts, Class c, S field) {
// indexed
IFieldIndex index = concepts.getFieldIndex(c, field);
if (index cast ConceptFieldIndexDesc) {
Map.Entry e = ((NavigableMap) index.valueToObject.data).lastEntry();
ret e == null ? null : (A) first((Cl) e.getValue());
}
ret lowestByField(field, concepts.list(c));
}