anchor.diff:              case Rs of 
                   [] ->
                       [{true, E}||{true, E}<-R];
  +                _  when R==[]->
  +                    zip_unification_results(Rs);
                   _ ->
                       [{true, E1++E2}||{true,E1}<-R, 
                                        {true,E2}<-zip_unification_results(Rs)]
  
positive.code:                             [{true, []}];
                         true -> [false]
                      end;
                  _ -> [{true, [{Exp1, Exp2}]}]
  	    end;
  	atom ->
              Exp1Val = wrangler_syntax:atom_value(Exp1),
  
negative.code:                                  false ->
                                       [];
                                   _ ->
                                       throw({error, lists:flatten(
                                                       io_lib:format
                                                         ("Condition checking of rule/collector "
                                                          "returns non-boolean value. Template being matched: ~s.",
                                                          [wrangler_prettypr:format(Exp1)]))})
                               end
                       end||{true,Subst}<-Res],
      case lists:append(PossibleMatches) of
  