anchor.diff:          % DifferenceOmissionTypes = message_types(Omissions) -- message_types(BaseOmissions),
           % debug("DifferenceOmissionTypes: ~p~n", [DifferenceOmissionTypes]),
   
  -        case EarlyOmissions andalso EarlyCausality andalso not lists:member(EarlyClassification, GenClassificationsExplored0) of
  +        case EarlyOmissions andalso EarlyCausality andalso not classification_explored(EarlyClassification, GenClassificationsExplored0) of
               true ->
                   debug("~n", []),
                   % debug("Entering generation pass.~n", []),
  
positive.code:         false ->
              invalid;
          true ->
              case lists:member(Classification, ClassificationsExplored0) andalso pruning() of  
                  true ->
                      debug("Classification: ~p~n", [Classification]),
                      debug("Classifications explored: ~p~n", [ClassificationsExplored0]),
  
negative.code:             false;
          _ ->
              true
      end.
  %% @private
  classification_explored(Classification, ClassificationsExplored) ->
      case Classification of 
          [] ->
              false;
          _ ->
              lists:member(Classification, ClassificationsExplored)
      end.
  