[fpc-pascal] Caller agnostic procedure variables

[Michael Van Canneyt]

On Tue, 15 Feb 2022, Michael Van Canneyt via fpc-pascal wrote:

>
>
> On Tue, 15 Feb 2022, Ryan Joseph via fpc-pascal wrote:
>
>>
>>
>>> On Feb 15, 2022, at 8:26 PM, Sven Barth via fpc-pascal 
> <fpc-pascal at lists.freepascal.org> wrote:
>>> 
>>> It's relatively "easy" to implement assigning a nested function to 
> function references. However assigning a nested function variable to a 
> function reference is much harder.
>>> Assigning a function reference to a nested function variable is hard as 
> well. 
>>> 
>>
>> I'm getting lost with the terms now I think. 
>> If your function takes a function reference parameter and you assign it a 
> nested function  pointer, 
>> this is difficult? I believe this was Michaels request in that code 
> snippet.
>
> Sven will need to confirm, but as I understand it:
>
> Procedure DoDemo(aTest : TProc);

For clarity, this should be something like:

Procedure DoDemo(aTest : TProc);

begin
   // Do stuff
   aTest;
end;

So the below procedures are not local to DoDemo...

Michael.

>
> Procedure MyTest;
>
>   Procedure DoSub;
>   begin
>   end;
>
> begin
>   DoDemo(DoSub)
> end;
>
> is easy.
>
> but
>
> Procedure DoDemo(aTest : TProc);
>
> Procedure MyTest;
>
> Var
>   ASub : procedure is nested;
>
> begin
>   aSub:=SomeFunctionThatReturnsANestedProc;
>   DoDemo(aSub);
> end;
>
> is difficult.
>
> Michael.
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