I want to add a Phobos module with template mixins for common idioms.

[Dmitry Olshansky]

23-May-2013 01:23, Idan Arye пишет:
> On Tuesday, 21 May 2013 at 17:40:02 UTC, Idan Arye wrote:
>> On Tuesday, 21 May 2013 at 14:58:16 UTC, Idan Arye wrote:
>>> At any rate, I am forced to admit I made a mistake about
>>> `hasIntance()` not needing synchronization. I neglected the
>>> possibility that the constructor(or anything else used for
>>> initialization) can throw!
>>>
>>> The compiler might decide that it's better to write the global
>>> reference first, and if the initializer throws just set it back to
>>> null. If that is the case, `hasInstance()` could see that the global
>>> reference is not null and return true, and then the initializer will
>>> throw and the initializing thread will set the global reference to
>>> null again.
>>>
>>> So yea, I'm gonna have to synchronize it too...
>>
>> OK, it is done.
>>
>> Next step - write the introduction. And then add the shared version of
>> the singleton.
>
> OK, I've written and pushed the documentation. I'll try to find
> somewhere to host the generated HTML.

I've found github pages to be just fine.

> I've also added `SharedSingleton` and renamed `LowLockSingleton` to
> `__GSharedSingleton` for consistency. I *did not* rename
> `ThreadLocalSingleton` to `StaticSingleton` - this will be too
> confusing("aren't all singletons static?").

Turns out that doing shared classes (and singletons conversely) has one 
big of disadvantage: you can't have TLS reference to shared class 
instance (ditto with mutable reference to const object).

It's a well-known problem of the way OOP is done in D - object and 
reference to it are tightly coupled and qualifier applies transitively 
to both.

There was a pull that allowed to separate qualifier of instance from 
reference (handle) looking like this:

ref const(Object) refToConst;

ref Object mutableTlsRef;
Object mutableTlsRef; //same as above

ref const Object constRefToConst;
const Object constRefToConst; //ditto

The fact that we don't have it is part of the reason I don't like doing 
OOP in D at all.

-- 
Dmitry Olshansky