Re: count matches in string, not region?

[Emanuel Berg]

Tassilo Horn wrote:

> Another way would be
>
>   (string-match-p "^[[:digit:]]\\{13\\}$" isbn)
>
> which returns non-nil iff isbn is a string of
> exactly thirteen digits.

Okay ... another way of doing ...?

Here is an example of an ISBN-10:

  0-13-308504-X

and here is an ISBN-13:

  978-91-0-011493-0

the check digit is the last one (X meaning 10,
and 0, respectively), so actually one only
needs 9 digits in the first case and 12 in
the second, to compute the check digit.

The groupings (...-...-...-...) do mean things
<https://dataswamp.org/~incal/books/isbn.txt>
but not with respect to how the check digit is
computed, so one can just drop dashes and all
chars that aren't digits.

More examples in the old file,
  https://dataswamp.org/~incal/emacs-init/isbn-verify.el

Thanks for the mail tho, I really want to close
the BOOK on this, so fire away all suggestion
you have :)

-- 
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