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

"Tim Bradshaw (as tfb at cley dot com)" <[email protected]> wrote:

> (what on earth is change-class & its machinery doing there? Don't
> answer: I know it is often used in the implementation of CLOS, but
> that is *not* a reason for it to exist at the user level.) and doesn't
> contain things that it should (I'd suggest sealing).

  CHANGE-CLASS at the user level is extremely useful, in particular to
compensate for the only problem CLOS has that you really can't work
around, namely equivalence between types, in the behavioral sense, and
classes, in the implementation sense (this is a deficiency of almost all
traditional object systems).

E.g. https://en.wikipedia.org/wiki/Circle%E2%80%93ellipse_problem
and this solution (look for slides 29 -- 32):
https://www.didierverna.net/lectures/paradigms/aop/05_advanced_clos.en.pdf


I also find it very convenient as a form of optimization, allowing you
to extend the capabilities of objects in-place (say, after acquiring
more information about them), as opposed to having to create new objects
based on the old ones.

-- 
Resistance is futile. You will be jazzimilated.

Lisp, Jazz, Aïkido: http://www.didierverna.info

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