Re: Local/temporary methods in CLOS

I need some way to define "local" methods, which can override
temporarily "global" methods and obey some kind of dynamic scoping rule.

>
I feel that your requirements may be somewhere in the locus of
Pastal Costanza's work, like ContextL.
>
https://github.com/pcostanza/contextl
>
Also see Costanza's paper "Dynamically Scoped Functions as the
Essence of AOP" [2003].

Thanks!  That's a nice solution, and the underlying implementation
technique makes a lot of sense (it refines the manual solution I've
been playing with).

Assuming I'm not the first to feel such a need, what are usual
approaches to try and provide that kind of behavior?

>
Since in Common Lisp we don't have dynamically scoped functions, only
variables, the straightforward thing, without using anyone's framework,
would be to use special variables to hold certain functions of interest,
and funcall them. (That can be wrapped or macroed over.)
>
(defun overridable-fun (&rest args)
  (apply *overridable-fun* args))
>
(let ((*overridable-fun* (lambda (...) ...)))
  (overridable-fun 42))

For dynamically-scoped local functions, that's indeed what I typically
use (or alternatively, I simply pass that function explicitly down the
stack), but my question is for the case where I want to do it for
methods, i.e. for "part" of a function (I guess I could simulate it by
overriding with a function that tests the args' type and delegates to the
old function, but then I get a kind of "linear-time" dispatch if there
are N local methods, which I'd rather avoid).


        Stefan