Re: Generators (iterators) for Gnu Emacs

[Stefan Monnier <monnier@iro.umontreal.ca>]

> I'd really rather signal to stop iteration. That way, it's harder to ignore
> end-of-iteration and loop forever and it remains possible to iterate over
> *any* value. condition-case is setjmp. I'm not *that* concerned by
> performance. The only other reasonable alternative is for iterators to
> yield a cons (terminal-p . value), and consing is going to be much worse
> than condition-case.

The alternative I was thinking was to return a unique value, as in:

   (defvar gen-eog (make-symbol "¡end-of-generator!"))
   (defun gen-eog-p (x) (eq x gen-oeg))

In terms of efficiency it should be fine (contrary to consing, indeed).


        Stefan