emacs: repeatable interactive commands

repeatable-zap-to-char.el

;; I happen to use a lot the command `zap-to-char', which prompts for
;; a character, and deletes from the point to the character,
;; included. However, it is not repetition friendly: when you call the
;; `repeat' command, you are prompted again for the character.

;; So, if you would like to zap to the character # four times, you
;; have to press

;; M-z # M-z # M-z # M-z # ; call repeatedly `zap-to-char'.
;; or
;; M-z # C-x z # z # z # ; zap-to-char, the call repeatedly `repeat'.

;; Hopefully, there is another way, without redefining `zap-to-char':

(let (my-zap-to-char-last-arg)
  (defun my-zap-to-char () ; make sure the command has no interactive argument
    "Repetition friendly version of `zap-to-char'."
    (interactive)
    (let ((arg (if (eq last-repeatable-command 'my-zap-to-char)
                   my-zap-to-char-last-arg
                 (setq my-zap-to-char-last-arg (read-char "zap to char: ")))))
      (zap-to-char 1 arg))))
(define-key global-map [remap zap-to-char] 'my-zap-to-char)

;; This works only in lexical binding mode. Otherwise you need to
;; define a global variable.

;; Now you can press:
;; M-z # M-z M-z M-z
;; or
;; M-z # C-x z z z

Weird, I thought repeat worked even for functions that took interactive input. This is disappointing.

It seems C-x ESC ESC can repeat zap-to-char with its input also. The issue is, C-x ESC ESC is itself not repeatable. Would have been nice otherwise.