anchor.diff:        first : TFieldDef;
       end;
   
  -  TFieldDef = class(TObj)
  +  TFieldDef = class
       public
         next : TFieldDef;
         name : TSymbol;
       end;
   
  -  TTuple = class(TObj)
  +  TTuple = class
       public
         meta : TTypeDef;
         data : TBytes;
  
positive.code: 
  type
    TEntry =  class;
    TDict  = class(TObj)
      public
        nextdict : TDict;
        latest   : TEntry;
        constructor Create;
        procedure Define( name : string; value : TObj );
        function Lookup( s : string; var item : TObj ): boolean;
      end;
  
    TEntry = class
      public
        prev : TEntry;
        name : string[32];
        item : TObj;
      end;
  
  
negative.code:     latest := en;
    end;
  
  function TDict.Lookup( s : string; var item : TObject): boolean;
    var en : TEntry; found : boolean;
    begin
      en := latest;
  