Re: How to convert an arbitrary string into a filename

[Platon Pronko]

On 2023-04-27 13:53, Eli Zaretskii wrote:
> > Date: Thu, 27 Apr 2023 07:52:55 +0300
> > From: Jean Louis <bugs@gnu.support>
> > Cc: help-gnu-emacs@gnu.org
> >
> > * Eli Zaretskii <eliz@gnu.org> [2023-04-26 16:09]:
> > > If you need to convert an accented character to its base character
> > > (i.e. "remove" the accent), Emacs has much more general facilities:
> > >
> > >    (require 'ucs-normalize)
> > >    (substring (ucs-normalize-NFKD-string "Ć") 0 1)
> > >     => "C"
> >
> > Alright, then like this:
> >
> > (defun string-slug (s &optional random)
> >    "Return slug for Website Revision System by using string S.
> >
> > RANDOM number may be added on the end."
> >    (let* ((random (or random nil))
> >          ;; (case-fold-search t)
> >           (s (replace-regexp-in-string "[^[:word:]]" " " s))
> >           (s (replace-regexp-in-string " +" " " s))
> >          (s (substring (ucs-normalize-NFKD-string s) 0 1))
> >           (s (replace-regexp-in-string "^[[:space:]]+" "" s))
> >           (s (replace-regexp-in-string "[[:space:]]+$" "" s))
> >           (s (replace-regexp-in-string " " "-" s))
> >          (s (if random (concat s "-" (number-to-string (random-number))) s)))
> >      s))
> >
> > (string-slug " OK, here, üößčć") ➜ ""
> >
> > It doesn't give good result.
>
> Of course.  Because you didn't understand how to use
> ucs-normalize-NFKD-string for your purposes.  Please read its doc
> string, and try to play with it, starting from the example I've shown.

I think something like this should work better:

(replace-regexp-in-string ucs-normalize-combining-chars-regexp "" 
(ucs-normalize-NFKD-string "Ć"))

The idea here is to replace "combined" codepoints with their Compatibility Decomposition, so instead of one 
"Ć" codepoint (0x0106) you will get "C" codepoint (0x43) followed by "combining acute 
accent" codepoint. Then you can regex-replace these combining characters and get the clean string.