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From: Nicolas Petton <nicolas@petton.fr>
To: Tino Calancha <tino.calancha@gmail.com>, 25929@debbugs.gnu.org
Cc: Stefan Monnier <monnier@iro.umontreal.ca>, tino.calancha@gmail.com
Subject: bug#25929: 25.2; map-delete doesn't delete permanently 1st alist elt
Date: Thu, 02 Mar 2017 11:59:08 +0100	[thread overview]
Message-ID: <87k288kkqr.fsf@petton.fr> (raw)
In-Reply-To: <87k288p2oq.fsf@gmail.com>

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Tino Calancha <tino.calancha@gmail.com> writes:


> (cl-loop for i below 3 collect
>   (let ((map (list (cons 0 3)
>                    (cons 1 4)
>                    (cons 2 5))))
>     (map-delete map i)
>     (null (map-elt map i))))
> => (nil t t) ; The first pair, i.e. '(0 . 3) is not permanently deleted.
>
> I've used the word 'permantly' because it seems it is temporary
> deleted:
>
> (cl-loop for i below 3 collect
>   (let ((map (list (cons 0 3)
>                    (cons 1 4)
>                    (cons 2 5))))
>     (null (map-elt
>            (map-delete map i)
>            i))))
> => (t t t)

The alist is indeed modified within the `map-delete' function, but in an
unexpected way: if the first key is deleted, the variable `map' is
`setq'ed, which has no effect outside of the function.

One fix would be to make `map-delete' a macro:

(defmacro map-delete (map key)
  "Delete KEY from MAP and return MAP.
No error is signaled if KEY is not a key of MAP.  If MAP is an
array, store nil at the index KEY.

  MAP can be a list, hash-table or array."
    `(macroexp-let2 nil key
       (map--dispatch ,map
         :list (setf (alist-get ,key ,map nil t) nil)
         :hash-table (remhash ,key ,map)
         :array (and (>= ,key 0)
                     (<= ,key (seq-length ,map))
                     (aset ,map ,key nil)))
       ,map))

WDYT?

Cheers,
Nico

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  parent reply	other threads:[~2017-03-02 10:59 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-02  7:17 bug#25929: 25.2; map-delete doesn't delete permanently 1st alist elt Tino Calancha
2017-03-02  8:56 ` Nicolas Petton
2017-03-02 10:59 ` Nicolas Petton [this message]
2017-03-02 11:30   ` Tino Calancha
2017-03-02 12:27     ` Nicolas Petton
2017-03-02 12:34   ` Nicolas Petton
2017-03-02 13:34     ` Tino Calancha
2017-03-02 15:12     ` Stefan Monnier
2017-03-04  0:04       ` Michael Heerdegen
2017-03-04  0:16         ` Michael Heerdegen
2017-03-21 20:41         ` Lars Ingebrigtsen
2017-03-22 11:55           ` Michael Heerdegen
2017-03-22 12:01             ` Lars Ingebrigtsen
2017-03-22 12:56               ` Noam Postavsky
2017-03-22 13:31                 ` Lars Ingebrigtsen
2017-03-22 14:43                   ` Michael Heerdegen
2017-03-22 17:04                   ` Stefan Monnier
2017-03-22 17:23                     ` Lars Ingebrigtsen
2017-03-22 20:31                       ` Stefan Monnier
2017-03-22 17:02               ` Stefan Monnier
2017-03-29 15:25             ` bug#25929: 25.2; plists and map-* Lars Ingebrigtsen
2017-03-29 15:36               ` Nicolas Petton
2017-03-21 11:35       ` bug#25929: 25.2; map-delete doesn't delete permanently 1st alist elt Nicolas Petton
2017-03-21 15:11         ` Stefan Monnier
2017-03-21 18:06           ` Nicolas Petton
2017-03-21 20:29             ` Stefan Monnier
2017-04-26  7:58               ` Nicolas Petton
2017-03-02 12:36   ` npostavs
2017-03-02 12:45     ` Nicolas Petton
2022-04-26 13:34 ` Lars Ingebrigtsen
2022-04-28  3:17   ` Richard Stallman
2022-04-28 16:00     ` Drew Adams

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