On Wed, Nov 27, 2013 at 1:51 AM, Frank Shearar <frank.shearar@gmail.com> wrote:

I realise that we never have "immutable with a capital I", hence why I
used the term "purely functional" to try work around the ambiguity
[1]. But the point is that Chris thinks that all Numbers behave like
SmallInteger, Boolean and Point in that they are, indeed, "immutable
by convention". It sounded to me like Levente was saying that this was
not true. If there are Numbers that are not "immutable by convention"
we should _make_ them immutable by convention ASAP!

Agreed. But note that there are edge cases in this apparently straight-forward case. The LargeIntegers need to be mutable while they're being constructed (they're not all constructed by primitive code and that primitive code is optional).

But on the "we will never have immutable with a capital I" point I disagree. The VM can easily enforce immutability. I actually implemented this for the Newspeak interpreter VM in 2007. It is a "small matter" of implementation to move it into Cog. It's probably two weeks work. But its not a priority yet. It might be a good thing to introduce when we move to Spur because there will be other things that will disturb too (image segments, ephemerons to be used, etc).

frank

[1] "Immutable with a capital I" requires VM support, IIRC

On 26 November 2013 22:45, Nicolas Cellier
<nicolas.cellier.aka.nice@gmail.com> wrote:
> What Levente says is that this immutability is purely conventional and not
> guaranteed.
> Numbers are technically mutable (but SmallInteger).
> Though, I strongly suggest to not play with such mutations, a mutant Number
> would be a frightening thing mathematically speaking...
>
>
> 2013/11/26 Frank Shearar <frank.shearar@gmail.com>
>>
>> On 26 November 2013 18:02, Levente Uzonyi <leves@elte.hu> wrote:
>> > On Tue, 26 Nov 2013, commits@source.squeak.org wrote:
>> >
>> >> Chris Muller uploaded a new version of Kernel to project The Trunk:
>> >> http://source.squeak.org/trunk/Kernel-cmm.821.mcz
>> >>
>> >> ==================== Summary ====================
>> >>
>> >> Name: Kernel-cmm.821
>> >> Author: cmm
>> >> Time: 26 November 2013, 10:24:26.281 am
>> >> UUID: 591c1ede-81bc-40d7-8591-af7fe29b2bd5
>> >> Ancestors: Kernel-fbs.820
>> >>
>> >> - Don't let Boolean and Number inherit Object's really slow
>> >> #veryDeepCopy.
>> >
>> >
>> > Some Numbers are mutable objects, so this doesn't sound right.
>>
>> Which Numbers are mutable? They _should_ all be purely functional,
>> like Point (which I know is not a Number).
>>
>> frank
>>
>> > Levente
>> >
>> >
>> >>
>> >> =============== Diff against Kernel-fbs.820 ===============
>> >>
>> >> Item was added:
>> >> + ----- Method: Boolean>>veryDeepCopy (in category 'copying') -----
>> >> + veryDeepCopy
>> >> + "Overridden for performance to avoid #fixDependents."
>> >> + ^ self!
>> >>
>> >> Item was added:
>> >> + ----- Method: Number>>veryDeepCopy (in category 'private') -----
>> >> + veryDeepCopy
>> >> + "Overridden for performance."
>> >> + ^ self!
>> >>
>> >>
>> >>
>> >
>>
>
>
>
>

--
best,

Eliot