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Fyodor:
thanks a lot. I was confused because they say that the old style
Oberon declarations are no longer necessary. You remember, these
RecordDesc and POINTER TO RecordDesc from the original Oberon?
I noted mentally that this is now gone and one can just use
POINTER everywhere.
My problem was that I need the RECORD, not pointer to record,
because Controls do not take pointers.
I now wrote the following and it now compiles, but I do not know
if it works or not. Recently I was bitten by the BlackBox Dialog/Control
pair, so now I am bracing for another round of hidden problems.
MODULE DanomTest;
IMPORT Stores, Dialog;
TYPE
PT* = RECORD (Stores.Store)
tree*: Dialog.Tree
END;
PPT = POINTER TO PT; (*note that not exported*)
(*Note that the following are exported, even though PPT is not.
Is this not surprising??*)
PROCEDURE (ppt: PPT) Internalize-(VAR rd: Stores.Reader);
END Internalize;
PROCEDURE (ppt: PPT) Externalize-(VAR wr: Stores.Writer);
END Externalize;
END DanomTest.
Wojtek Skulski skulski{([at]})nowhere.xy
On Wed, 2 Jul 2003 ftkachov{([at]})nowhere.xy
> Dear Wojtek,
>
> This is certainly not a bug.
> One cannot change the signutare in the overriding method
> except by narrowing the receiver type and the function result type.
>
> Stores.Store is a pointer, and In/Externalize are defined with
> the pointer as receiver, so one cannot use a VAR record there.
>
> Perhaps if the language now allows one to define
> a pointer type extending a record type and vice versa,
> it might be logical that it should be allowed
> to use either pointer or a variable as the receiver.
>
> But perhaps there are hidden obstacles for that?
>
> Cheers
> Fyodor Tkachov
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Received on Wed Jul 02 2003 - 04:03:01 UTC