sclass GazelleEngine implements IGazelleEngine {
  F0<GazelleEvalContext> contextMaker;
  
  public LS answer(S s, O... _) {
    ret collect line(dm_reasonWithPreAndPost(s,
      paramsPlus(_,
        contextMaker := assertNotNull(contextMaker))));
  }
  
  public LS preprocess(S s, O... _) {
    null;
  }
}