Re: limited agregate and limited components default initialization

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2018-04-02 21:46, Jere wrote:
> On Monday, April 2, 2018 at 2:51:00 PM UTC-4, Dmitry A. Kazakov wrote:
>> On 2018-04-02 20:19, Jere wrote:
>>
>>> Something else unrelated to your question, but that I just noticed: Assuming
>>> you could have gotten a list definition that you were happy with, there is
>>> still a very serious problem with it.  Doubly linked lists (ones that use
>>> both Next and Prev/Pred) are susceptible to "circular references" when using
>>> reference counting smart pointers.  You would need to use a weak reference
>>> based smart pointer for one of the two (either Next or Prev/Pred, whichever
>>> you prefer).
>>>
>>> -- very simple/silly example
>>> type Node is
>>>      Value : Item_Type;
>>>      Next  : Smart_Pointer_Type;
>>>      Prev  : Weak_Smart_Pointer_Type;
>>> end Node;
>>
>> This is still circular. Weak/strong references work only in hierarchical
>> structures. If a doubly-linked list must deploy them then it should be
>> the head holding references to all nodes. It does not make much sense
>> though.
>>
> Nope, not circular at all unless you connect Tail to Head (which isn't
> the normal use case).

Usually I do, it makes operations faster and easier because links are 
never null. I can even have not-null constraint on the links.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de