[fpc-pascal] Case in Record

[Anton Tichawa]

On Tue, 2009-10-06 at 23:37 +0800, 章宏九 wrote:
> Thank you. I saw all the examples you gave, but I still cannot master
> how to use a variant record without a specified tag.
> 
> For example:
> type
>   TShapeList = (Rectangle, Triangle, Circle, Ellipse, Other);
>   TFigure = record
>     case TShapeList of
>       Rectangle: (Height, Width: Real);
>       Triangle: (Side1, Side2, Angle: Real);
>       Circle: (Radius: Real);
>       Ellipse, Other: ();
>   end;
> var
>   Figure1: TFigure;
> 

AFAIK there has to be some fixed part before the variant, e. g.

TFigure = record
    name: string;
    case TShapeList of
      Rectangle: (Height, Width: Real);
      Triangle: (Side1, Side2, Angle: Real);
      Circle: (Radius: Real);
      Ellipse, Other: ();
  end;

The program could then determine from the contents of the "name" field
which variant is used in a certain instance. This saves memory ("TShapeList"
has no memory reserved at run time), but the program is responsible
to correctly identify the variant using the "name" field.

Anton