unofficial mirror of bug-guix@gnu.org 
 help / color / mirror / code / Atom feed
From: Leo Prikler <leo.prikler@student.tugraz.at>
To: "Ludovic Courtès" <ludo@gnu.org>
Cc: 45570@debbugs.gnu.org, conjaroy@gmail.com
Subject: bug#45570: [PATCH] system: Assert, that user and group names are unique.
Date: Wed, 06 Jan 2021 13:34:26 +0100	[thread overview]
Message-ID: <e1f7d49f48db237ece4527a8ee5236a8bfa629e7.camel@student.tugraz.at> (raw)
In-Reply-To: <87v9cao0c8.fsf@gnu.org>

Hi,

Am Mittwoch, den 06.01.2021, 10:56 +0100 schrieb Ludovic Courtès:
> Hi,
> 
> Leo Prikler <leo.prikler@student.tugraz.at> skribis:
> 
> > *gnu/system/shadow.scm (find-duplicates): New variable.
> > (assert-unique-account-names, assert-unique-group-names): New
> > variables.
> > (account-activation): Use them here.
> 
> [...]
> 
> > +(define (find-duplicates list =)
> > +  (match list
> > +    ('() '())
> 
> This should be:
> 
>   (match list
>     (() '())
>     …)
> 
> I’m surprised '() works as a pattern.
I think it's because matching literals works, but you're right.

> > +    ((first . rest)
> > +     (if (member first rest =) ; (srfi srfi-1) member
> > +         (cons first (find-duplicates rest =))
> > +         (find-duplicates rest =)))))
> 
> Note that this is quadratic; it’s fine as long as we don’t have “too
> many” users, which may be the case in general.
It is indeed quadratic, but would there even be an n log n solution?
I've once done an n log n sort+delete-duplicates!, perhaps that'd be a
nicer solution here?

> > +(define (assert-unique-account-names users)
> > +  (for-each
> > +   (lambda (account)
> > +     (raise (condition
> > +             (&message
> > +              (message
> > +               (format #f (G_ "account with name '~a' found
> > twice.")
> > +                       (user-account-name account)))))))
> > +   (find-duplicates users (lambda (alice bob)
> > +                            (string=? (user-account-name alice)
> > +                                      (user-account-name bob))))))
> 
> ‘for-each’ looks awkward since we’ll stop on the first one.  How
> about
> something like:
> 
>   (define (assert-unique-account-names users)
>     (match (find-duplicates things …)
>       (() #t)
>       (lst
>        (raise (formatted-message (G_ "the following accounts appear
> more than once:~{ ~a~}~%"
>                                  lst))))))
> 
> ?
That'd be weird for duplicate duplicates, hence just reporting the
first.  Of course we could always count occurrences by allocating a
local hash table and then do some fancy hash-map->list conversion.  If
we do use hash-tables, perhaps this could even be a linear algorithm?

Regards,
Leo





  reply	other threads:[~2021-01-06 12:35 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-12-31 18:14 bug#45570: operating-system definitions allow duplicate passwd and group entries Jason Conroy
2021-01-01 11:13 ` bug#45570: [PATCH] system: Assert, that user and group names are unique Leo Prikler
2021-01-02  1:16   ` Danny Milosavljevic
2021-01-02  5:57 ` Leo Prikler
2021-01-06  9:56   ` Ludovic Courtès
2021-01-06 12:34     ` Leo Prikler [this message]
2021-01-06 13:32       ` Ludovic Courtès
2021-01-06 21:00         ` Leo Prikler
2021-01-07  8:29           ` Ludovic Courtès
2021-01-06 21:21 ` bug#45570: [PATCH v2] " Leo Prikler
2021-01-07  8:35   ` Ludovic Courtès
2021-01-07 11:13     ` Leo Prikler
2021-01-07 11:10 ` bug#45570: [PATCH v3] " Leo Prikler
2021-01-11 13:09   ` Ludovic Courtès
2021-01-11 15:06     ` Leo Prikler

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: https://guix.gnu.org/

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=e1f7d49f48db237ece4527a8ee5236a8bfa629e7.camel@student.tugraz.at \
    --to=leo.prikler@student.tugraz.at \
    --cc=45570@debbugs.gnu.org \
    --cc=conjaroy@gmail.com \
    --cc=ludo@gnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://git.savannah.gnu.org/cgit/guix.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).