On Mon, Mar 09, 2020 at 06:02:40PM +0100, Ludovic Courtès wrote:
> To me it’s not a bug in Guile, but simply the fact that regexps, as
> implemented by the C library, are locale-dependent.
> 

(use-modules (ice-9 regex))
(regexp-exec (make-regexp "^([a-z]+)$")
             "iyiyim")
⇒ #f

Guile’s behavior that i is not among [a-z] has been confirmed as
unexpected by a natively Turkish friend of mine.  It is different from
the behavior of current glibc:

florian@florianmacbook ~$ cat iyiyim.c
#include <regex.h>
#include <stdio.h>
#include <stdlib.h>
#define STR "iyiyım"
int main (int    argc,
          char** argv)
{
  regex_t only_letters;
  int r = regcomp (&only_letters, "[a-z]+", REG_EXTENDED);
  if (r != 0)
    printf ("This error does not happen.\n");
  r = regexec (&only_letters, STR, 1, malloc (sizeof (regmatch_t)), 0);
  if (r == 0)
    printf ("The string " STR " matched!\n");
  else
    printf ("No match for " STR ".\n");
}
florian@florianmacbook ~$ gcc -o iyiyim iyiyim.c
florian@florianmacbook ~$ LANG=tr_TR.utf8 ./iyiyim 
The string iyiyım matched!

Apparently Guile uses a bundled regular expression library rather than
glibc.  I can try making Guile use a newer GNUlib for its regular
expressions, maybe that helps.  Shall I file a separate bug for Guile?

> The patch you proposed looks good to me, though perhaps we could
> explicitly list all the alphabet in the regexp?
> 
> A better option is to reimplement ‘store-path-package-name’ in a way
> similar to ‘store-path-hash-part’, as in commit
> 35eb77b09d957019b2437e7681bd88013d67d3cd.

I suppose it would be better to cache the compiled regexp.  What is
this mcached syntax inside (guix store)?  Or do I use Scheme’s 'delay'
and 'force' for caching?

The attached patch fixes the regexp.  Shall I push the attached patch
and then try making it cache the compiled regexp or do you still
prefer an implementation without regexps?  Why would not using a
regexp be better?

Regards,
Florian