The "no gc" crowd

[Walter Bright]

On 10/10/2013 10:54 AM, Andrei Alexandrescu wrote:
> On 10/10/13 12:18 AM, Walter Bright wrote:
>> On 10/9/2013 11:34 PM, Jacob Carlborg wrote:
>>> On 2013-10-10 02:22, Sean Kelly wrote:
>>>
>>>> Only that this would have to be communicated to the user, since
>>>> moving data
>>>> later is problematic. Today, I think it's common to construct an
>>>> object as
>>>> unshared and then cast it.
>>>
>>> What is the reason to not create it as "shared" in the first place?
>>
>> 1. Shared data cannot be passed to regular functions.
>
> I don't understand this. If a function/method accepts "shared", then it can be
> passed shared data.

I meant regular functions as in they are not typed as taking shared arguments. 
Shared cannot be implicitly cast to unshared. I say regular because very, very 
few functions are typed as accepting shared arguments.



>> 2. Functions that create data structures would have to know in advance
>> that they'll be creating a shared object. I'm not so sure this would not
>> be an invasive change.
>
> There is no other way around it. And this is not a change - it's fixing something.

I'm not convinced of that at all.


>> 3. Immutable data is implicitly shared. But it is not created immutable
>> - it is created as mutable data, then set to some state, then cast to
>> immutable.
>
> That all must happen in the runtime, NOT in user code.
>
>
> Andrei
>