Re: limited agregate and limited components default initialization

[Jere <jhb.chat@gmail.com>]

On Sunday, April 1, 2018 at 7:39:19 PM UTC-4, Jean-Claude Rostaing wrote:
> Ok, now I know why what I wanted to do was impossible. To store an object into an accessor or whatever, or to create it with allocator, with only a given "value" of this limited type, you need to COPY this value, whatever you do. Which goes against the very idea of limited type.
> I feel more intelligent thanks to that...
> And I know why though ITEM_TYPE is indefinite limited, you can only translate from its POINTER to a smart pointer, never directly from a value of that limited type.

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;