Re: Arbitrary function: find the number(s) of expected arguments

[Davis Herring]

> This way `my-foo' automagically accepts callbacks that expect one argument
> (as in initial form), as well as those that want two arguments.

What if your existing clients might have

(defun paul-callback (computed-data &optional cached)
  ...)

where they make calls to `paul-callback' themselves with the extra 
argument?  It's fair to call this "abstruse" (maybe most/all clients 
just use a lambda), but it might also make you think about providing 
another callback interface.

Davis

--
This product is sold by volume, not by mass.  If it appears too dense or 
too sparse, it is because mass-energy conversion has occurred during 
shipping.