How to turn this C++ into D?

[luminousone via Digitalmars-d-learn]

On Wednesday, 5 November 2014 at 20:31:54 UTC, Patrick Jeeves 
wrote:
> On Wednesday, 5 November 2014 at 19:44:57 UTC, luminousone 
> wrote:
>> On Wednesday, 5 November 2014 at 19:05:32 UTC, Patrick Jeeves 
>> wrote:
>>> On Wednesday, 5 November 2014 at 18:56:08 UTC, luminousone 
>>> wrote:
>>>> unless delete is explicitly called, I don't believe the 
>>>> destructor would ever be called, it would still have a 
>>>> reference in the static foo_list object that would stop it 
>>>> from being collected by the gc.
>>>
>>> This is exactly why I asked about it, and even if delete is 
>>> explicitly called-- which i believe is deprecated, wouldn't 
>>> the runtime fill the space with the default construtor until 
>>> the GC decides to remove it? meaning it would be immediatly 
>>> added back into the list?
>>
>> I don't believe that the default constructor is called. I am 
>> pretty sure delete immediately deallocates the object, 
>> deregistering its memory from the gc.
>>
>> In fact I am 99% sure no constructor is called after delete, 
>> it would cause problems for objects with no default 
>> constructor, or for system related stuff done in constructors, 
>> and I haven't seen anything like that in my X11 work in d.
>
> I guess I got confused by something... I don't know.  But what 
> I'd really like is for it to be garbage colleceted when no 
> references outside of that static array exist, as i mentioned 
> at the bottom of my first post.  I illustrated my example with 
> that specific class because when i looked up "weak pointers" on 
> the site I found discussions getting caught up with how to 
> avoid dangling pointers when weak pointers are used; and I 
> wanted to illustrate that that's a non-issue in this case, 
> because I wasn't sure how much that contributed to the 
> solutions given.
>
> I suppose it doesn't matter because this is based on something 
> I do with multiple inheritance in C++, I felt like I may be 
> able to get it to work in D because the only public members of 
> those classes were always pure virtual functions.
>
> As an aside, how does scope(success) work in the context of a 
> constructor? given:
>
> abstract class foo
> {
>     this()
>     {
>        scope(success) onAdd();
>     }
>     ~this()
>     {
>        onRemove();
>     }
>
>     onAdd();
>     onRemove();
> }
>
> class bar : foo
> {
>     int _a;
>
>     this(int a)
>     {
>        _a = a;
>     }
>
>     void onAdd()    { writeln(_a); }
>     void onRemove() { writeln(_a); }
> }
>
> is _a defined as anything in either of writes? or would it be 
> called at the wrong time relative to setting _a?

As of yet their are no built in weak references/pointers, you can 
jerry rig them however.

constructors will implicitly call super at the top of the 
function if no super call is made within the function body, so

this( int a ) {
     // <---- super(); is called here if not defined below
     _a = a;
}

> I'd really like is for it to be garbage colleceted when no 
> references outside of that static array exist, as i mentioned 
> at the bottom of my first post.

Can't easily do this yet, would require you writing your own list 
class, as std.container, does not have any way of passing an 
allocator to it.

They are coming, slowly but surely we will eventually have them.

Allocators would allow container classes to create objects(nodes 
and such) that are in memory that is not scanned by the garbage 
collector.

You can in fact allocate memory manually right now, via 
std.c.memory or std.c.stdlib (don't member which one has c malloc 
and free).

Just be sure to familiarize your self with the manual gc 
registration and deregistration functions in core.memory.