GNU bug report logs - #50290
Using `setf` on `map-elt` repeats evaluation for returning the value of `setf`

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Package: emacs;

Reported by: Okamsn <okamsn <at> protonmail.com>

Date: Tue, 31 Aug 2021 02:59:01 UTC

Severity: normal

Fixed in version 28.1

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

Bug is archived. No further changes may be made.

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Report forwarded to bug-gnu-emacs <at> gnu.org:
bug#50290; Package emacs. (Tue, 31 Aug 2021 02:59:02 GMT) Full text and rfc822 format available.
Acknowledgement sent to Okamsn <okamsn <at> protonmail.com>:
New bug report received and forwarded. Copy sent to bug-gnu-emacs <at> gnu.org. (Tue, 31 Aug 2021 02:59:02 GMT) Full text and rfc822 format available.

Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Okamsn <okamsn <at> protonmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Using `setf` on `map-elt` repeats evaluation for returning the value
 of `setf`
Date: Tue, 31 Aug 2021 02:58:11 +0000

Hello,

When I do `(setf (map-elt map key) (my-func))`, it expands to

     (let* ((key key))
       (condition-case nil
           (with-no-warnings
             (map-put! map key (my-func) nil))
         (map-not-inplace
          (setq map (map-insert map key (my-func)))
          (my-func))))

The repetition of `(my-func)` raises warnings.  Compare with using
`(setf (alist-get key map) (my-func))`, where the result of `(my-func)`
is bound to `v` so that it is only called once:

     (let* ((p (if (and nil (not (eq nil 'eq)))
                   (assoc key map nil)
                 (assq key map)))
            (v (my-func)))
       (progn
         (if p
             (setcdr p v)
           (setq map (cons (setq p (cons key v))
                           map)))
         v))

This is on Emacs 28 with Map.el 3.1.
Information forwarded to bug-gnu-emacs <at> gnu.org:
bug#50290; Package emacs. (Wed, 01 Sep 2021 08:34:01 GMT) Full text and rfc822 format available.

Message #8 received at 50290 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Okamsn <okamsn <at> protonmail.com>
Cc: 50290 <at> debbugs.gnu.org
Subject: Re: bug#50290: Using `setf` on `map-elt` repeats evaluation for
 returning the value of `setf`
Date: Wed, 01 Sep 2021 10:33:10 +0200

Okamsn <okamsn <at> protonmail.com> writes:

> When I do `(setf (map-elt map key) (my-func))`, it expands to
>
>      (let* ((key key))
>        (condition-case nil
>            (with-no-warnings
>              (map-put! map key (my-func) nil))
>          (map-not-inplace
>           (setq map (map-insert map key (my-func)))
>           (my-func))))
>
> The repetition of `(my-func)` raises warnings. 

Yup.  This should now be fixed on the trunk.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no
bug marked as fixed in version 28.1, send any further explanations to 50290 <at> debbugs.gnu.org and Okamsn <okamsn <at> protonmail.com> Request was from Lars Ingebrigtsen <larsi <at> gnus.org> to control <at> debbugs.gnu.org. (Wed, 01 Sep 2021 08:34:02 GMT) Full text and rfc822 format available.
bug archived. Request was from Debbugs Internal Request <help-debbugs <at> gnu.org> to internal_control <at> debbugs.gnu.org. (Wed, 29 Sep 2021 11:24:08 GMT) Full text and rfc822 format available.
This bug report was last modified 2 years and 208 days ago.

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