static L<GazelleTree> gazelle_reasonWithPreprocessing(S input1, O... _) {
  F0<GazelleEvalContext> contextMaker = cast assertNotNull("Need contextMaker", optPar contextMaker(_));
  S userName = stringPar userName(_);
  bool debug = boolPar debug(_);
  bool debugPreprocessing = boolPar debugPreprocessing(_);
  Collector<GInterpretable> interpretables_out = cast optPar interpretables_out(_);
  
  Collection<GInterpretable> interpretables = gazelle_preprocess(input1, _);
  
  if (debugPreprocessing) {
    print("Got " + n2(interpretables, "interpretable") + ".");
    printIndentLines(interpretables);
  }
  
  if (interpretables != null) addAll(interpretables_out, interpretables); 
  
  Set<S> acceptablePurposes = cast optPar acceptablePurposes(_);
  if (acceptablePurposes == null) acceptablePurposes = litset("");
  
  new L<GazelleTree> l2;
  Set<S> outputs = ciSet();

  for (GInterpretable intp : interpretables) {
    L<GazelleTree> results = dm_gazelle_reasonAboutChatInput_v2(userName, intp.text, paramsPlus(_, +acceptablePurposes));
    print(intp.text + " => " + n2(results, "result"));
    for (GazelleTree tree : results)
      if (outputs.add(tree.line)) {
        if (tree.mr != null) tree.mr.interpretable = intp;
        l2.add(tree);
      }
  }
  
  gazelle_dropMatchedDefaultRules(l2, _);
  
  ret l2;
}