invariant/const class storage class

[Andrei Alexandrescu]

Simen Kjaeraas wrote:
> On Thu, 02 Oct 2008 03:46:00 +0200, Andrei Alexandrescu 
> <SeeWebsiteForEmail at erdani.org> wrote:
> 
>> Simen Kjaeraas wrote:
>>> On Wed, 01 Oct 2008 16:23:32 +0200, Yigal Chripun 
>>> <yigal100 at gmail.com> wrote:
>>>
>>>> Andrei Alexandrescu wrote:
>>>>> Yigal Chripun wrote:
>>>>>> Walter Bright wrote:
>>>>>>> Simen Kjaeraas wrote:
>>>>>>>> Is this really correct behavior? How then are we supposed to
>>>>>>>> initialize our
>>>>>>>> invariant objects?
>>>>>>> Currently, create them as mutable ones, then cast them to invariant.
>>>>>>
>>>>>> I understand casting as breaking the type system. shouldn't there 
>>>>>> be a
>>>>>> way to create invariant objects without the cast?
>>>>>> an invariant constructor seems a good way to solve this. any plans on
>>>>>> adding such a feature to D2?
>>>>>
>>>>> There are plans.
>>>>>
>>>>>> I think it can work like this:
>>>>>>
>>>>>> class A {
>>>>>>   this(params) {}   // [1]
>>>>>>   invariant this(params) {}  // [2]
>>>>>> }
>>>>>>
>>>>>> // create a mutable object - will use type [1] c-tors.
>>>>>> auto a = new A(params);
>>>>>>
>>>>>> // create an invariant object - will use type [2] c-tors.
>>>>>> invariant a = new A(params);
>>>>>>
>>>>>> // create a const object - will use type [1] or [2] c-tors.
>>>>>> const a = new A(params);
>>>>>>
>>>>>> in the const case, if there are two c-tors which only differ by
>>>>>> invariant-ness of the c-tor using either will create ambiguity and
>>>>>> therefore should be a compile-time error.
>>>>>
>>>>> Way, way, way more complicated than this.
>>>>>
>>>>> Andrei
>>>>
>>>> May I ask what are the complications?
>>>  "Mortis Portalis Tackulatum - and he's still breathing"...
>>
>> Tackulatum? Was that tacitum?
>>
>> Andrei
>>
> 
>  From Terry Pratchett's 'Pyramids'.
> 
> Doctor: "Fairly straightforward. A case of mortis portalis tackulatum 
> with complications."
> Chidder: "What's that mean?"
> Doctor: "In laymen's terms, he's as dead as a doornail."
> Chidder: "What are the complications?"
> Doctor: "He's still breathing."

Heh. Funny, but what's the link?

Andrei