From: <tomas@tuxteam.de>
To: help-gnu-emacs@gnu.org
Subject: Re: `apply-partially` and hash tables
Date: Sun, 20 Oct 2024 11:54:04 +0200 [thread overview]
Message-ID: <ZxTTPLH+3feWmG/r@tuxteam.de> (raw)
In-Reply-To: <861q0b2jpo.fsf@fastmail.fm>
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On Sun, Oct 20, 2024 at 11:43:15AM +0200, Joost Kremers wrote:
> Hi list,
>
> A question that just came up: if I use `apply-partially` to create a
> function that has a hash table as one of its fixed arguments, and then at
> some later point add data to said hash table, it seems that this data is
> visible to subsequent calls to the partially applied function:
>
> ```
> (let* ((s #s(hash-table test equal data ("MGrt" "Mouton De Gruyter"
> "OTS" "Utrecht School of Linguistics UiL-OTS")))
> (fn (apply-partially #'parsebib--expand-strings s)))
> (puthash "BW" "Oxford: Blackwell Publishers" s)
> (funcall fn "BW"))
> "Oxford: Blackwell Publishers"
> ```
>
> `parsebib--expand-strings` is a function that (among other things) does a
> hash table look-up. The entry ("BW" "Oxford: Blackwell Publishers") is
> added to the hash table after the function is created, but it can obviously
> still be found by it.
>
> So my question: is this intended behaviour, something that I can rely on to
> continue to work, or is this an artefact of the implementation that may
> change at any time in the future?
This is an interesting question: it comes down to what can be considered
"immutable".
I guess a hash table doesn't count (as wouldn't a buffer, possibly a list
or any other object with a complex "inner life").
Cheers
--
t
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next prev parent reply other threads:[~2024-10-20 9:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-20 9:43 `apply-partially` and hash tables Joost Kremers
2024-10-20 9:54 ` tomas [this message]
2024-10-20 14:46 ` Stefan Monnier via Users list for the GNU Emacs text editor
2024-10-20 15:19 ` Joost Kremers
2024-10-20 17:04 ` Stefan Monnier
2024-10-20 19:12 ` Rudolf Schlatte
2024-10-20 20:29 ` Stefan Monnier via Users list for the GNU Emacs text editor
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