Re: using finalizers

[Stefan Monnier]

> You are probably taking the wrong assumption about the effect of letrec
>
> (macroexpand '(letrec ((more (make-finalizer close))
>                        (close (lambda ()
>                                 (setq bar t))))
>                 (lambda ()
>                   (when more
>                     (pop x)))))
>
> ==> (let (more close)
>          (setq more (make-finalizer close))
>          (setq close (lambda nil (setq bar t)))
>          (lambda nil (when more (pop x))))

Indeed, the code needs to swap `more` and `close`.

> I think Common Lisp doesn't have letrec in the standard. And you are
> proabaly taking the assumption that ELisp's letrec works as well as
> Scheme's one. But it is not.

I don't think Scheme's `letrec` works any differently in this respect,
except that instead of nil, variables get a special "void like" value
before they're initialized.

In the above code, the real bug I can see which we should fix is that
`make-finalizer` should signal an error if its arg is not a function.


        Stefan