[Vm-dev] Re: Immutability, newspeak (was: Vm-dev post from jbaptiste.arnaud@gmail.com requires approval)

[stephane ducasse]

Andreas

This is true that having this free bit is nice for experimenting.  Now the immutability bit would be really good to 
build immutable strings and other data types. We could for example ensure that string literal are not modified even if stored
in the literal frame. When we see the current trends in languages (erlang, newspeak...) it would be good to have it
but this is also true that we should build a real case before that so we are also in a bootstrap loop. Last time I checked point
and rectangle and they are functional by design so I'm curious to know what we could gain to make them immutable. 

Now eliot mentioned that he will get rid of compact class so we could get more bits.
Note that jean-baptiste did this work because eliot mentioned that we should extract it from newspeak if we want to get a chance
to have it in squeak/pharo.

Stef

On Jun 8, 2010, at 6:15 PM, Andreas Raab wrote:

> On 6/8/2010 7:41 AM, David T. Lewis wrote:
>> What do the VM developers think with respect adopting the VM changes?
>> The immutability bit is a scarce resource. Is it OK to allocate it
>> for this purpose or are there likely to be other projects interested
>> in using it for other reasons?
> 
> Honestly, I don't thinnk the immutability bit carries its weight here. There's some fun stuff you can do with it, for sure, but outside of *extremely* specialized applications (oodbs) there will be little to no use for it. At least I don't see where you'd make use of immutability in some random app that's not a database. If it were essentially free to add it, I wouldn't mind (like I said there's fun stuff that one can do) but given that we're talking about allocating a header bit I feel that there's just not enough mileage we get out of it...
> 
> Just my random $.02.
> 
> Cheers,
>  - Andreas