// first parameter can be Concepts
svoid indexConceptFields(O... params) {
  int i = 0;
  Concepts c;
  if (first(params) instanceof Concepts) {
    c = (Concepts) first(params);
    ++i;
  } else c = db_mainConcepts();
  for (; i < l(params); i += 2)
    indexConceptField(concepts, (Class) params[i], (S) params[i+1]);
}