static <A extends Concept> L<A> findConceptsWhere(Class<A> c, O... params) {
  ret findConceptsWhere(mainConcepts, c, params);
}

static L<Concept> findConceptsWhere(S c, O... params) {
  ret findConceptsWhere(mainConcepts, c, params);
}

static <A extends Concept> L<A> findConceptsWhere(Concepts concepts, Class<A> c, O... params) {
  params = expandParams(c, params);
  
  // indexed
  if (concepts.fieldIndices != null)
    for (int i = 0; i < l(params); i += 2) {
      IFieldIndex<A, O> index = concepts.getFieldIndex(c, (S) params[i]);
      if (index != null) {
        print("Using index");
        new L<A> l;
        for (A x : index.getAll(params[i+1]))
          if (checkConceptFields(x, params)) l.add(x);
        ret l;
      }
    }
    
  // table scan
  ret filterConcepts(concepts.list(c), params);
}

static L<Concept> findConceptsWhere(Concepts concepts, S c, O... params) {
  ret filterConcepts(concepts.list(c), params);
}