Smart references

via Digitalmars-d digitalmars-d at
Sat Mar 14 08:55:49 PDT 2015

On Friday, 13 March 2015 at 15:21:42 UTC, Zach the Mystic wrote:
> On Wednesday, 11 March 2015 at 20:33:07 UTC, Andrei 
> Alexandrescu wrote:
>> I'm investigating D's ability to define and use smart 
>> references. Per the skeleton at 
>>, lines:
>> #6: You can't default-initialize a ref.
>> #7: You can't copy a ref - copying should mean copying the 
>> object itself.
>> #9: Per this example I'm hooking a reference with an Owner. 
>> The reference hooks calls to opAddRef and opRelease in the 
>> owner.
>> #23: Assigning the reference really assigns the referred.
>> #28: A reference is a subtype of ref T. Most operations 
>> against the reference will be automatically forwarded to the 
>> underlying object, by reference ("ref" is important here).
>> As unittests show, things work quite nicely. There are a few 
>> things that don't:
>> #70: Attempting to copy a reference fails on account of the 
>> disabled postblit. There should be a way to tell the compiler 
>> to automatically invoke alias this and create a copy of that 
>> guy.
>> #81: Moving from a reference works by moving the Ref object. 
>> There should be a way to tell the compiler that moving should 
>> really move the payload around.
>> There are a couple other issues not represented in the 
>> unittest, for example related to template deduction. In a 
>> perfect world, Ref would masquerade (aside from having a 
>> different layout, ctor, and dtor) as an lvalue of type T.
>> But in fact I think solving the matters above would go a long 
>> way toward making smart references nicely usable. Although my 
>> example is centered on reference counting an owner, there are 
>> other uses of smart references. Are all these worth changing 
>> the language?
> Are the suggested changes also related to the possibility of 
> making `ref` a type?

Are there plans to do this? I remember Walter suggested `ref` for 
non-parameters, i.e. local variables, but as a storage class, not 
a type modifier.

More information about the Digitalmars-d mailing list