// returns number of changes

static int cset_compareByStruct(Concept c, O... values) ctex {

  int changes = 0;

  values = expandParams(c.getClass(), values);

  warnIfOddCount(values);

  for (int i = 0; i+1 < l(values); i += 2) {

    S field = (S) values[i];

    O value = values[i+1];

    Field f = setOpt_findField(c.getClass(), field);

    //print("cset: " + c.id + " " + field + " " + struct(value) + " " + f);

    if (value instanceof RC) value = c._concepts.getConcept((RC) value);

    value = deref(value);

    if (value instanceof S && l((S) value) >= concepts_internStringsLongerThan) value = intern((S) value);

    if (f == null) {

      // TODO: keep ref if it exists

      mapPut2(c.fieldValues, field, value instanceof Concept ? c.new Ref((Concept) value) : value);

      c.change();

    } else if (isSubtypeOf(f.getType(), Concept.Ref.class)) {

      ((Concept.Ref) f.get(c)).set((Concept) derefRef(value));

      c.change(); ++changes;

    } else {

      O old = f.get(c);

      if (!structEq(value, old)) {

        f.set(c, value);

        if ((f.getModifiers() & java.lang.reflect.Modifier.TRANSIENT) == 0) c.change(); 

        ++changes;

      }

    }

  }

  ret changes;

}