Re: [fpc-pascal] [PATCH] Addition of OnNotify event on "TFPGObjectList" and "TFPGList" triggered on the insert, delete and extract methods.

[denisgolovan]

Hi

 

That always keeps me wondering - why neither FPC, no any other mainstream static-type language implements specialization based not only on types, but on compile-time constants as well?

 

I mean something like

 

  TGenericList<T,options> = class

    ...

  end;

 

procedure TGenericList<T,options>.Delete(index:integer);

begin

  if (nnNotifyDelete in options) and Assigned(FOnDelete) then

     FOnDelete(...);

  end;

end;

 

// usage

type

  TMyList = specialize TGenericList<integer, [nnNotifyAdd, nnNotifyDelete, nnNotifyChange]>;

 

... that "if (nnNotifyDelete in options) " condition will optimized out by compiler if options lack corresponding enum constant.

Of course, FOnDelete property should be omitted as well in ideal case. That might require something like "static if" in D.

 

I've done that trick for ages using m4 preprocessor and it works really good, why it's still not supported natively by compilers themselves?

 

20.02.2016, 02:05, "Sven Barth" <pascaldra...@googlemail.com>:

There's no need for a sample. This degradation is the whole reason why the non-generic classes TFPObjectList and TFPList exist compared to TObjectList and TList which do have notifications.

Regards,
Sven

,

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--
Regards,

Denis Golovan

 

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