anchor.diff:  -include("dderl.hrl").
   -include("dderl_sqlbox.hrl").
   
  --define(DefCollInd,10).  % First indentation level which will be collapsed by default
  +-define(DefCollInd,6).  % First indentation level which will be collapsed by default
  +-define(DefCollLen,40). % Max length of flattened subboxes which is collapsed
   
   -spec validate_children([#box{}]) -> ok | {error, binary()}.
   validate_children([]) -> ok;
  
positive.code: 
  -ifdef(DefCollInd).
  -undef(DefCollInd).
  -define(DefCollInd,10).
  -endif.
  
  %% TESTS ------------------------------------------------------------------
  
negative.code: pretty_from_box(#box{ind=Ind,name= <<>>,children=CH}) ->
      if
          (hd(CH))#box.collapsed ->
              % ?Info("collapsed box ~p ~p",[<<>>,CH]),                
              iolist_to_binary([indent(Ind+1),[flat_from_box(C) || C <-CH],"\r\n"]);
          true ->
              % ?Info("expanded box ~p ~p",[<<>>,CH]),                
              iolist_to_binary([[pretty_from_box(C) || C <-CH]])
      end;
  pretty_from_box(#box{collapsed=true}=Box) -> flat_from_box(Box);  % moved down from top to be revisited
  pretty_from_box(#box{ind=Ind,name=Name,children=CH}) ->
      if
          (hd(CH))#box.collapsed ->
              % ?Info("collapsed box ~p ~p",[Name,CH]),                
              iolist_to_binary([indent(Ind),binary_to_list(Name),"\r\n",
                  indent(Ind+1),[flat_from_box(C) || C <-CH],"\r\n"]);
          true ->
              % ?Info("expanded box ~p ~p",[Name,CH]),                
              iolist_to_binary([indent(Ind), Name,"\r\n",[pretty_from_box(C) || C <-CH]])
      end;
  pretty_from_box([Box|Boxes]) ->
  