GNU bug report logs - #25929
25.2; map-delete doesn't delete permanently 1st alist elt

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Package: emacs;

Reported by: Tino Calancha <tino.calancha <at> gmail.com>

Date: Thu, 2 Mar 2017 07:19:01 UTC

Severity: normal

Found in version 25.2

Fixed in version 29.1

Done: Lars Ingebrigtsen <larsi <at> gnus.org>

Bug is archived. No further changes may be made.

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From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Nicolas Petton <nicolas <at> petton.fr>
Cc: 25929 <at> debbugs.gnu.org, Tino Calancha <tino.calancha <at> gmail.com>
Subject: bug#25929: 25.2; map-delete doesn't delete permanently 1st alist elt
Date: Thu, 02 Mar 2017 10:12:09 -0500

>     (macroexp-let2 nil key
>       `(progn
>          (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)))

Note that this will make it pretty much impossible to use
cl-generic dispatch.

A better option might be to provide a map-remove which works
functionally (i.e. doesn't modify its argument by side-effects), and
then change map-delete to signal an error when we ask to delete the
first element of the list (and to stop returning the "new map" since it
just works imperatively instead).


        Stefan
This bug report was last modified 3 years and 27 days ago.

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