;;; -*- lexical-binding: t -*-
;;
;; this file:
;;   https://dataswamp.org/~incal/emacs-init/enum.el

(require 'cl-lib)
(require 'subr-x)

(defun enum (&optional beg end suf)
  "Enumerate each line from BEG to END, counting from one.
Use SUF as a suffix to the digits inserted.
BEG defaults to the beginning of the buffer,
END defaults to the end of the buffer,
SUF defaults to \". \""
  (interactive
   `(,@(if (use-region-p)
           (list (region-beginning) (region-end))
         (list nil nil) )
     ,(when current-prefix-arg
        (read-string "suffix: ") )))
  (or beg (setq beg (point-min)))
  (or end (setq end (point-max)))
  (or suf (setq suf ". "))
  (goto-char beg)
  (let*((lines   (count-lines beg end))
        (pad-len (length (number-to-string lines))) )
    (cl-loop
      for line from 1 to lines
      do (goto-char (line-beginning-position))
         (insert
           (format "%s%s"
                   (string-pad (number-to-string line) pad-len nil t) suf) )
         (forward-line) )))

(provide 'enum)