Re: How to read an integer from the minibuffer

[Gregory Heytings]

> I'd like to read an integer (or something else e.g. matching a regex) 
> from a minibuffer.  Basically, I'm after a version of `read-string', but 
> either allowing only some characters, or accepting only input matching 
> some regex (possibly both).
>
> How do I do that?  One way would be to use `read-from-minibuffer' with a 
> suitable keymap, but that seems slightly low-level.  If that is the way 
> to go, is there a good way to set up a keymap so that nothing except 
> some specified characters are self-inserting?  IOW, is `suppress-keymap' 
> the way to go or is there some other way?

(defun restricted-read-from-minibuffer (prompt allowed-chars)
  "Read a string from the minibuffer, prompting with PROMPT.
The only allowed characters are those in the string ALLOWED-CHARS."
  (let ((m (make-keymap)))
    (define-key m [t] #'ignore)
    (define-key m (kbd "RET") #'exit-minibuffer)
    (define-key m (kbd "<return>") #'exit-minibuffer)
    (define-key m (kbd "C-j") #'exit-minibuffer)
    (define-key m (kbd "C-g") #'abort-minibuffers)
    (dolist (c (split-string allowed-chars "" t))
      (define-key m c #'self-insert-command))
    (read-from-minibuffer prompt nil m)))