Re: tail recursion hack in Emacs Lisp?

[Oliver Scholz <alkibiades@gmx.de>]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> So my question is: Can anybody think of a case where this approach
>> would break?
>
> I have another question: why is it better than CL's `do' ?

Huh?  You mean like:

(do ((n 10 (1- n))
     (r 1 (* n r)))
    ((= n 1) r))

I had no intention to suggest that it were better. iterate/named
let is just different. Personally I find `do' hard to read, but
that might be a matter of taste.

I used `fact' just because it is the classical example. I can't
think of a really good example right now, exept maybe this:

(defun my-flatten-list (lst)
  (iterate walk-list ((lst lst)
		      (acc nil)
		      (stk nil))
    (if (null lst)
	(if (null stk)
	    (nreverse acc)
	  (walk-list stk acc nil))
      (if (listp (car lst))
	  (walk-list (car lst)
		     acc
		     (if (null (cdr lst))
			 stk
		       (cons (cdr lst)
			     stk)))
	(walk-list (cdr lst)
		   (cons (car lst) acc)
		   stk)))))

There might be better examples. To quote the CMU CL manual: "The
main advantage of using iterate over do is that iterate naturally
allows stepping to be done differently depending on conditionals
in the body of the loop."

    Oliver
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