[squeak-dev] Towards a more consistent and sensible implementation of #isAbstract

Nicolas Cellier nicolas.cellier.aka.nice at gmail.com
Sun Dec 10 10:09:04 UTC 2017

2017-12-10 9:53 GMT+01:00 Marcel Taeumel <marcel.taeumel at hpi.de>:

> So it comes down to what "being abstract" actually means in the
> environment. :-) I think it means #== considering the current VM and the
> role of classes. Not sure in a the generic, object-oriented sense, though.
> Best,
> Marcel
> Am 10.12.2017 00:02:06 schrieb Chris Muller <asqueaker at gmail.com>:
> With objects you should delegate to the the receiver to decide what #=
> means -- which in most cases will inherit that default implementation from
> Object anyway.  Sending #== is generally bad form.
> Converting uses of #= to #== for "performance" is a bad idea except in the
> most inner, performance-critical code, and even then, it should be with a
> comment.
> Absolutely, if it's only for the sake of optimization, it's a bad decision.
Not to mention that isAbstract is not performance critical at all.

Maybe the intention is to really test for identity.
That's because we have the knowledge that classes are the unique instance
of their metaclass.
So using = could be seen as an un-necessary indirection.

Reducing the level of indirection may reduce complexity.
But it is also reducing extensibility as noted by Marcel.

But do we want to elimiate complexity at all?
I see this related to "complex versus complicated" and the original
biological analogy.
Are resilient/adptative systems necessarily complex?
If so, ideally such complex system should be built from simple
What we want to avoid if possible is complicated things.


> On Thu, Dec 7, 2017 at 2:30 AM, Marcel Taeumel <marcel.taeumel at hpi.de>
> wrote:
>> Hi, there.
>> What are your thoughts on how to implement "MyClass class >>
>> #isAbstract"? I think that one should always use #== and compare it to an
>> actual class object like this:
>> MyClass class >> #isAbstract
>>    ^ self == MyClass
>> At the time of writing, we have various attempts in your image. You can
>> browse them easily:
>> Best,
>> Marcel
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