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
_______________________________________________
fpc-pascal maillist - fpc-pascal@lists.freepascal.org
http://lists.freepascal.org/mailman/listinfo/fpc-pascal
