[fpc-pascal] Option type

Ryan Joseph genericptr at gmail.com
Tue Jun 1 20:51:03 CEST 2021



> On Jun 1, 2021, at 12:20 PM, denisgolovan via fpc-pascal <fpc-pascal at lists.freepascal.org> wrote:
> 
> Hi all
> 
> I am trying to implement Option<T> type in FPC.
> 
> type
>  generic TOption<T> = record
>    case IsSome:boolean of
>    true: ( some: T );
>    false: ();
>  end;

You need to use a constraint like:

type
 generic TOption<T: TObject> = record
   case IsSome:boolean of
   true: ( some: T );
   false: ();
 end;

Not sure why though.

Regards,
	Ryan Joseph



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