[Vm-dev] Re: [squeak-dev] The Trunk: System-eem.803.mcz
Jan van de Sandt
jvdsandt at gmail.com
Thu Mar 3 12:50:42 UTC 2016
Hello,
In VA Smalltalk it is also possible to mark an object as readonly. VA
Smalltalk uses the following method names::
#isReadOnly
#markReadOnly: aBoolean
If you try to update a readonly object you get a PrimErrReadOnly error.
Jan.
On Thu, Mar 3, 2016 at 1:34 PM, Clément Bera <bera.clement at gmail.com> wrote:
>
> Hello,
>
> I agree that there is a naming problem. However, we decided to let it this
> way because that is the VisualWorks terminology and we wanted to be
> compatible.
>
> We can do two things:
> - change the image-side APIs only, which is easy to do (#isImmutable =>
> #isReadOnly and co).
> - change the terminology in the VM, which is a bit more complex and error
> prone.
>
> So if, and only if, there is a community agreement on a new terminology, I
> think we could change at least the image-side.
>
> I like the isReadOnly or hasWriteBarrier terminologies myself, but I
> don't mind if the community decides to choose another terminology.
>
> Regards
>
> Clement
>
> 2016-03-03 11:08 GMT+01:00 Tobias Pape <Das.Linux at gmx.de>:
>
>>
>>
>> On 03.03.2016, at 09:56, Eliot Miranda <eliot.miranda at gmail.com> wrote:
>>
>> >
>> > Hi Tobias,
>> >
>> >> On Mar 3, 2016, at 12:10 AM, Tobias Pape <Das.Linux at gmx.de> wrote:
>> >>
>> >>
>> >> Hi all, Hi Eliot, Hi Clément
>> >>
>> >> Well, you know I'm the opponent here regarding the Immutability naming.
>> >> I hate that I have to come back to the naming thing here once again.
>> >> But it is rather important for me, since I work on immutability
>> concepts
>> >> that are unlike what immutability would mean here. I think it is also
>> >> important to know that immutability in most other languages means
>> >> "it won't change whatsoever" (including OCaml[1], Racket[2],
>> >> Haskell[3], or object-oriented programming in general[4])
>> >>
>> >> Now, I see the need, usefulness, and practical implementation for
>> objects
>> >> that cannot be written and hence throw an error, which _then_ can be
>> >> circumvented/made be writable. I'm all for it and I like it. Except
>> >> for the name.
>> >>
>> >> As Clément put it:
>> >> "As argued on the virtual machine mailing list, we are talking
>> >> about a write-barrier more than immutability itself."
>> >>
>> >>
>> >> I would hence propose to name those objects
>> >>
>> >> locked objects
>> >>
>> >> with the accompanying Someone-tries-to-write-that-Error named
>> >>
>> >> ObjectIsLockedError
>> >>
>> >> and the state-change messages
>> >>
>> >> Object>>lock
>> >> Object>>unlock
>> >>
>> >> and likewise the VM-information
>> >>
>> >> SmalltalkImage>>supportsLockedObjects
>> >>
>> >> I know, re-iterating this is tedious, but it will avoid unmet
>> >> expectations by newcomers from other languages as well as
>> >> name clashes with actual immutability implementations (how should
>> >> we name those, then)?
>> >
>> > No need to apologize. I had forgotten the naming issue in my delight
>> at fixing the actual VM issue and being able to get an
>> immutability^h^h^h^h^h^h^h^h^h^h^h^hwrite-protect fault. Forgive me.
>>
>> I completely understand that
>>
>> >
>> > But locked is definitely the wrong word. To me it evokes notions of
>> mutual exclusion and concurrency.
>>
>> Yeah, but I thought more of the 'door lock' lock.
>> What about latch? It fits the the door lock metaphor but also the
>> electronic meaning fits:
>> "a circuit which retains whatever output state results from a momentary
>> input signal until reset by another signal."
>>
>> Best regards
>> -Tobias
>>
>> > Tomorrow I'll rename the accessors etc to use the term read-only, so
>> supportsReadOnlyObjects, beReadOnly isReadOnly and setReadOnly:. Ok with
>> you? Any objections y'all?
>>
>>
>>
>> >
>> >>
>> >> With apologies
>> >> -Tobias
>> >>
>> >>
>> >> [1]: http://typeocaml.com/2015/01/02/immutable/
>> >> [2]: a) http://docs.racket-lang.org/reference/pairs.html "Pairs are
>> not mutable"
>> >> b) http://docs.racket-lang.org/reference/strings.html
>> >> [3]:
>> https://wiki.haskell.org/A_brief_introduction_to_Haskell#Immutable_declarations
>> >> [4]: https://en.wikipedia.org/wiki/Immutable_object
>> >>
>> >>> On 03.03.2016, at 03:19, commits at source.squeak.org wrote:
>> >>>
>> >>> Eliot Miranda uploaded a new version of System to project The Trunk:
>> >>> http://source.squeak.org/trunk/System-eem.803.mcz
>> >>>
>> >>> ==================== Summary ====================
>> >>>
>> >>> Name: System-eem.803
>> >>> Author: eem
>> >>> Time: 2 March 2016, 7:18:21.713694 pm
>> >>> UUID: 934ce776-0717-469b-8818-300954393791
>> >>> Ancestors: System-bf.802
>> >>>
>> >>> Add getters that answer whether the VM supports immutability or
>> multiple bytecode sets.
>> >>>
>> >>> =============== Diff against System-bf.802 ===============
>> >>>
>> >>> Item was added:
>> >>> + ----- Method: SmalltalkImage>>supportsImmutability (in category
>> 'system attributes') -----
>> >>> + supportsImmutability
>> >>> + "Answer whether the VM observes the per-object immutability flag
>> and consequently
>> >>> + aborts writes to inst vars of, and fails primitives that
>> attempt to write, to immutable objects."
>> >>> + "SmalltalkImage current supportsImmutability"
>> >>> +
>> >>> + ^(self vmParameterAt: 65)
>> >>> + ifNil: [false]
>> >>> + ifNotNil:
>> >>> + [:param| "In older VMs this is a boolean reflecting
>> MULTIPLE_BYTECODE_SETS"
>> >>> + param isInteger "In newer VMs it is a set of integer
>> flags, bit 1 of which is IMMUTABILITY"
>> >>> + ifTrue: [param anyMask: 2]
>> >>> + ifFalse: [false]]!
>> >>>
>> >>> Item was added:
>> >>> + ----- Method: SmalltalkImage>>supportsMultipleBytecodeSets (in
>> category 'system attributes') -----
>> >>> + supportsMultipleBytecodeSets
>> >>> + "Answer whether the VM supports multiple bytecodeSets."
>> >>> + "SmalltalkImage current supportsMultipleBytecodeSets"
>> >>> +
>> >>> + ^(self vmParameterAt: 65)
>> >>> + ifNil: [false]
>> >>> + ifNotNil:
>> >>> + [:param| "In older VMs this is a boolean reflecting
>> MULTIPLE_BYTECODE_SETS"
>> >>> + param isInteger "In newer VMs it is a set of integer
>> flags, bit 0 of which is MULTIPLE_BYTECODE_SETS"
>> >>> + ifTrue: [param anyMask: 1]
>> >>> + ifFalse: [param]]!
>> >>
>>
>>
>
>
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