[fpc-pascal] pointer to anything

[tcoq at free.fr]

1° Using the root class TObject might be a good alternative?
Storing any object within the structure is easy.
Getting the object back will need a type overwrite.

2° Concerning standard structures, you might want to look at TList, TObjectList,
TInterfacedList, TComponentList, TStringList which provide a lot.
TStringList is very easy to use as a hash list in fact.

3° There are additional structured types in the FCL

4° You might want to read "Tomes of Delphi: Algorithms and data structures". See
this link:
http://www.amazon.com/Tomes-Delphi-Algorithms-Data-Structures/dp/1556227361
The source code attached is interesting.

5° You might want to investigate the generics in FPC, since thyey're very useful
to build typed containers.

5° Stay away from untyped types, they're (mostly) dangerous. Basically, it means
your requirements or design has not been sufficiently investigated.
Using precise types in Pascal is, in fact, a huge advantage. You will have been
warned.

Hope this helps,
Thierry
Selon ik <idokan at gmail.com>:

> Try the following:
>
> type list = ^node;
>    node = record
>        data : Variant;
>        next : list;
>    end;
>
>
> Variant can store a lot pf data types, however please note that it's very
> slow type.
> You also must remember that Pascal is Strong typed, unlike C or duck type
> languages.
>
> The Pointer type store only memory address and not the data itself, so it's
> not recommended to use it unless you control the memory allocation itself
> for each 'data'.
>
> Ido
>
> http://ik.homelinux.org/
>
>
> 2010/4/23 spir ☣ <denis.spir at gmail.com>
>
> > Hello,
> >
> > Say I want to implement a kind of linked list which node data may be
> > anything. Thus I cannot store data on place (in nodes), indeed; so it
> should
> > be referenced. But pointers themselves are supposed to be typed. So, how
> can
> > I do that?
> >
> > type list = ^node;
> >    node = record
> >        data : ???;
> >        next : list;
> >    end;
> >
> > I tried to use Pointer, but then I get an error saying the compiler found
> > <some type> while it expected "untyped". What is the use of Pointer
> (without
> > type for pointed data)?
> > I also had a look at Variant; this looks like an ugly hack ;-) And avyway
> > is not really generic. I need data to ba able to be anything, including
> > first a linked list itself...
> > Finaly, when trying to write the the algo for a given type, I get an issue
> > since the def above is recursive, recursively pointing in fact. So, I need
> > to stop the run somewhere by allocating the memory for non-yet-existing
> data
> > pointed by a pointer -- I guess.
> >    p^ := <I'll tell you soon, just book the place>
> > (The compiler warns about not initialised pointers.)
> >
> > Pointers (sic!) to implementations of similar things (including trees)
> > welcome...
> > More generally, I cannot find in the library units for common data
> > structures (sequence, associative table, set (the collection)...).
> >
> > Denis
> > ________________________________
> >
> > vit esse estrany ☣
> >
> > spir.wikidot.com
> > _______________________________________________
> > fpc-pascal maillist  -  fpc-pascal at lists.freepascal.org
> > http://lists.freepascal.org/mailman/listinfo/fpc-pascal
> >
>