Emacs Lisp: The iota function for number ranges in Emacs Lisp

Emacs Lisp: The iota function for number ranges in Emacs Lisp

This is the iota function that I had to make today. I have shamelessly borrowed the description from Guile reference manual on iota function from SRFI-1 and tried to make it compliant. I guess this could be done more elegantly. For me is important that it gives me the same result as intended.

Thus (iota 10) would evaluate to (0 1 2 3 4 5 6 7 8 9).

(iota 10 1) would evaluate to (1 2 3 4 5 6 7 8 9 10).

And (iota 10 1 2) would evaluate to (1 3 5 7 9 11 13 15 17 19).

The behavior is the same as in SRFI-1.

By using this iota function I can generate the number range and then iterate over the list with the dolist' function. I could then iterate with(dolist (num (iota 10 20)))` from the number 20 to number 29.

(defun iota (count &optional start step)
  "Return a list containing COUNT numbers, starting from START
and adding STEP each time.  The default START is 0, the default
STEP is 1"
  (let* ((start (if start start 0))
     (step (if step step 1))
     (last (+ start count))
     (counter 0)
     (list '())
     (elt start))
    (while (< counter count)
      (push elt list)
      (setq elt (+ elt step))
      (setq counter (1+ counter)))
    (reverse list)))

iota is often used in Scheme programming language. Guile and other scheme implementations already have it, and I have got used to it. There probably exists in Emacs lisp equivalent function or somebody else already made it, but I do not know anything about it. I had to make it myself.

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