anchor.diff:    FFormula := '';
   end;
   
  +procedure TmGroupByDef.Assign(const aSource: TmGroupByDef);
  +begin
  +  FFieldName:= aSource.FieldName;
  +  FDataType := aSource.DataType;
  +  FOperationKind := aSource.OperationKind;
  +  FFormula := aSource.Formula;
  +end;
  +
   { TmCalculationDef }
   
   constructor TmCalculationDef.Create;
  
positive.code:     FFormula : String;
    public
      constructor Create;
  
      property FieldName : string read FFieldName write FFieldName;
      property DataType : TFieldType read FDataType write FDataType;
  
negative.code:   public
      constructor Create;
      destructor Destroy; override;
      procedure Assign(const aSource : TmGroupByDefs);
  
      function Add : TmGroupByDef;
      function Count : integer;
  