Re: Help with recursive destructive function

[Michael Heerdegen]

I wrote:

> I guess I would use an iterator: the definition would still looks
> recursive, but the execution isn't problematic any more if done right.

Here is an example:

#+begin_src emacs-lisp
(iter-defun iter-tree-example (tree)
  (cl-loop for thing in-ref tree by #'cdr do
           (if (consp thing)
               (iter-yield-from (iter-tree-example thing))
             (iter-yield
              (ignore
               (when (stringp thing)
                 (cl-callf upcase thing)))))))

(let ((tree '("a" 1 ("b" "c" ("d")) "e")))
  (iter-do (_ (iter-tree-example tree)))
  tree)
==>
 ("A" 1
   ("B" "C"
    ("D"))
   "E")

(let ((huge-list (number-sequence 1 100000)))
  (setcdr (last huge-list) (cons "a" nil))
  (iter-do (_ (iter-tree-example huge-list)))
  (ignore huge-list))
|-- takes some time but doesn't crash
#+end_src

Yield values don't have any purpose but I guess without yielding you
would get no CPS rewrite but a standard recursive function that would be
problematic with the HUGE-LIST.


Michael.