Thanks!
I thought that T^^.next was equivalent to T^.next.^next.
This helps me very much to move on and understand.
On Wed, 15 Dec 2004 02:32:15 GMT, "Jason Burgon"
wrote:
> wrote in message
>news:ogvur0t6iidgaf3ipeb1rnu5vje5beh6h5@4ax.com...
>> Hi,
>>
>> I understand the use of the ^ in pointers and how pointers work in
>> TP7. I recently came accross soem code where they haev for example:
>>
>> T^^.next
>>
>> I have used it in the form of T^.next when traversing a linked list.
>> Am just not sure how the double carets are to be used.
>
>It simply means that T is a pointer to pointer, and double-dereferencing is
>indeed often used by linked-list code. For example:
>
>type
> PDirectory = ^TDirectory;
> TDirectory = object
> Next: PDirectory;
> Children: PDirectory;
> ....;
> end;
>
> function TDirectory.AddChild(D: PDirectory): Boolean;
> var
> PCur: ^PDirectory;
> begin
> if D = nil then
> begin
> AddChild := False;
> Exit;
> end;
> PCur := @Children;
> while (PCur^ <> nil) and (DosCompare(D^.Name^, PCur^^.Name^) = 1) do
> PCur := @PCur^^.Next;
> D^.Next := PCur^;
> PCur^ := D;
> AddChild := True;
> end;
>
>Note that the intial value for PCur is set to the address of the pointer
>that contains the address of the first in the linked-list of Children. The
>use of double-dereferencing here ellimitates the need to handle the
>otherwise special case of dealing with the first element of the list.
>
>> Also I have seen @ being used instead of NEW,
>
>No you haven't. New allocates heap memory to an object and returns a pointer
>to it. @ returns the address of an existing object.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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