count matches in string, not region?

[Emanuel Berg via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>]

This [last] I wrote a couple of nights ago, it
is part of my ISBN stuff [1] that will soon be
a MELPA package, God willing. But more on that
if and when it happens...

Anyway as you see the 4th line doesn't look
good, instead of moving the point one would
like to invoke the/a count function with the
already-fetched isbn-as argument.

So is there a count-matches-in-string or
something to that extent anywhere, that you are
aware of?

3.1415-out

(defun check-isbn-at-point ()
  (interactive)
  (let*((isbn-string (thing-at-point 'symbol t))
        (num-digits (count-matches "[[:digit:]]" (point) (progn (forward-symbol 1) (point))))
        (check-digit (if (> num-digits 10)
                         (checksum-isbn-13 isbn-string)
                       (checksum-isbn-10 isbn-string) )))
    (message "check digit: %s" check-digit)
    ))
(defalias 'ciap #'check-isbn-at-point)


[1] https://dataswamp.org/~incal/emacs-init/isbn-new.el

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