elisp - How to write a key bindings in emacs for easy repeat?

Question

Let's say I bind the key to a certain function as follows:

(global-set-key (kbd "C-c =") 'function-foo)

Now, I want the key binding to work as:
After I press C-c = for the first time, if I want to repeat the function-foo, I don't need to press C-c again, but simply repeat pressing =. Then, after I call the function-foo for enough times, I can just press keys other than = (or explicitly press C-g) to quit.

How to do this?

Answer 1

This may be the thing you are looking for:

(defun function-foo ()
  (interactive)
  (do-your-thing)
  (set-temporary-overlay-map
    (let ((map (make-sparse-keymap)))
      (define-key map (kbd "=") 'function-foo)
      map)))