Re: MOP question for language lawyers: can you specialize on standard-class

I have been listening with keen interest to this topic. 

My understanding is that class instance slot access seems to be slow because of the desired versatility of the MOP? If that is the case, I had discussions at lunch, perhaps 30 years ago, with David Robson of the Xerox Parc team that did Smalltalk-80. And I distinctly recall him discussing the new technology of JIT compiling and caching. I had thought that CLOS incorporated similar strategies.



> On May 26, 2026, at 01:18, Tim Bradshaw (as tfb at cley dot com) <[email protected]> wrote:
> 
> On 18 May 2026, at 15:20, [email protected] wrote:
>> 
>> Anyway, I don’t like participating in discussions where somebody is “exaggerating for effect.” That reminds me too much of the bad days in comp.lang.lisp. Feel free to have the final word in our exchange.
> 
> I'm sorry, I didn't intentionally exaggerate for effect.
> 
> What I am trying to say is this:
> 
> Some aspects of CLOS (slot access for one thing) are *significantly* slow.  CLOS is about 40 years old, so I think that if it could have been made fast it would have been by now.  So I infer that this is because of something to do with the design of CLOS.
> 
> Julia's object system is not slow, but it is not correct to say it has 'solved it' in the sense that we could just use what Julia does in CLOS (this is what I thought you meant when you said that), because Julia's object system is significantly different to CLOS.
> 
> So the interesting question is: what could be done to CLOS to make it quick?  And in particular can anything be done *without compromises*?  I believe the answer to that is no, it can't: to make slot access quick in CLOS you would need to make promises that you will not use various features of it.
> 
> That's what Dylan did, for instance.
> 
> --tim
> 
> 
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