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?

Another way:

(defun restricted-read-from-minibuffer (prompt regexp)
  "Read a string matching REGEXP from the minibuffer, prompting with PROMPT."
  (let ((s nil))
    (while (progn
             (setq s (read-from-minibuffer prompt))
             (unless (string-match regexp s)
               (message "Unexpected input.")
               (sit-for 1)
               t)))
    s))