[fpc-pascal] about dynamic array

[spir ☣]

On Fri, 7 May 2010 06:10:30 +0200
cobines <cobines at gmail.com> wrote:

> 2010/5/6 spir ☣ <denis.spir at gmail.com>:
> > (By the way, started playing with TFPList already, and could not find how to get data back! I mean the symtric of add(). Even tried indexing (who knows, with the syntactic magic of modern language? ;-).)
> 
> It is indexing.
> 
> var
>   l: TFPList;
>   p: Pointer;
>   index: Integer;
> begin
>   l := TFPList.Create;
>   index := l.Add(p);
>   p := l[index];
> end;
> [...]

Thank you, I must have written a typo or messed up indices, since now it works fine. Still, remains a mystery about untyped pointers, illustrated by the code below:

var
	l : TFPList;
	i : Integer;
	p : ^Integer;
begin
	l := TFPList.Create;
	i := 1 ; new(p) ; p^ := i; l.Add(p);
	p := l[0] ; writeln(p^);
	writeln(l[0]^);			// error
end.

I cannot directly "fish" and use the pointer's target. Seems I always need to pass _via_ the pointer, then all is fine. It's not really annoying. But I don't understand the difference: in code, both versions are indeed strictly equivalent. I guess there's an implicit (pointer?) conversion somewhere?
Are there cases where the pointer's mediation is not needed?

Denis
________________________________

vit esse estrany ☣

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