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From: Philip Kaludercic <philipk@posteo.net>
To: "Alfred M. Szmidt" <ams@gnu.org>
Cc: arthur.miller@live.com,  emacs-devel@gnu.org
Subject: Re: cond* vs pcase
Date: Tue, 06 Feb 2024 16:50:02 +0000	[thread overview]
Message-ID: <87o7cttu4l.fsf@posteo.net> (raw)
In-Reply-To: <E1rXO89-0003Ll-3B@fencepost.gnu.org> (Alfred M. Szmidt's message of "Tue, 06 Feb 2024 11:17:05 -0500")

"Alfred M. Szmidt" <ams@gnu.org> writes:

>    "Alfred M. Szmidt" <ams@gnu.org> writes:
>
>    >    I use pcase often; but I use it just as a better cond. For example I find this
>    >    handy:
>    >
>    >    (defvar foo nil) <-- foo is some symbol
>    >
>    >    (pcase foo
>    >      ('bar (do-some-bar-stuff))
>    >      ('baz (do-some-baz-fluff)))
>    >
>    > cl-case seems more appropriate here (wish cl-case was just case ...)
>
>    Why more appropriate?
>
> Because your not doing pattern matching, you're comparing against a
> set of strings/symbols/numbers/....

Simply because pattern matching is a more powerful generalisation,
capable of expressing case-distinction; in the end it compiles down to
almost the same code anyway.

>    I always think of pcase as Elisp's case.  In
>    addition, pcase avoids the danger of naively writing 
>
>       (cl-case foo
> 	('bar (do-some-bar-stuff))
> 	('baz (do-some-baz-fluff)))
>
>    and then getting surprised when foo evaluates to `quote'.
>
> Suprises will happy, you will get suprises with pcase and cond* too --
> I find it suprising that to match over symbols requires pattern
> matching.  One might also question why you (well, no you specifically)
> are comparing against (quote bar) etc?  That is a suprise in it self...

I don't understand your point here.  If one expects the cases to be
evaluated, then quoting makes sense if you want to match a symbol.  It
is not true, but common enough that the byte compiler emits a warning.

>    >    or this:
>    >
>    >    (setq foo "some-string")
>    >
>    >    (pcase foo
>    >      ("foo" (do-foo-case))
>    >      ("bar" (do-bar-case)))
>    >
>    > Same here, with (intern foo) ...
>
>    Being able to do equal instead of eql is also something that speaks in
>    favour of pcase...
>
> It speaks more in favor of having CASE where you can change the
> comparison operator or a CASE-STRING or similar, not something much
> more generic pcase (or even cond*!) -- i.e. why use pcase/cond* when
> you're not using any of the features that are the main point of those
> two macros.

I am sorry, but I don't follow your point here either.  Is the general
claim, that one should only use whatever exactly and at most satisfies
the needs at hand?



  parent reply	other threads:[~2024-02-06 16:50 UTC|newest]

Thread overview: 46+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-05 14:30 cond* vs pcase Arthur Miller
2024-02-05 15:13 ` Eli Zaretskii
2024-02-05 16:06 ` Alfred M. Szmidt
2024-02-05 18:39   ` Philip Kaludercic
2024-02-06 12:30     ` Arthur Miller
2024-02-06 16:17     ` Alfred M. Szmidt
2024-02-06 16:35       ` [External] : " Drew Adams
2024-02-06 16:50       ` Philip Kaludercic [this message]
2024-02-06 17:27         ` Alfred M. Szmidt
2024-02-06 18:57           ` Philip Kaludercic
2024-02-06 19:04             ` Alfred M. Szmidt
2024-02-06 19:39               ` Philip Kaludercic
2024-02-06 23:17                 ` [External] : " Drew Adams
2024-02-06 19:12             ` Drew Adams
2024-02-06 20:08               ` Adam Porter
2024-02-06 23:32                 ` Drew Adams
2024-02-07 13:14                   ` Arthur Miller
2024-02-07 13:43                     ` Po Lu
2024-02-07 17:09                       ` Drew Adams
2024-02-07 17:44                       ` Tomas Hlavaty
2024-02-09  3:52                         ` Richard Stallman
2024-02-07 18:00                       ` Arthur Miller
2024-02-07 18:22                         ` Alfred M. Szmidt
2024-02-08  1:55                           ` Po Lu
2024-02-08  2:49                             ` Philip Kaludercic
2024-02-08  3:36                               ` Po Lu
2024-02-08  7:04                             ` Eli Zaretskii
2024-02-08 17:01                               ` Alfred M. Szmidt
2024-02-08 17:01                             ` Alfred M. Szmidt
2024-02-09  1:30                               ` Po Lu
2024-02-08  5:01                         ` Po Lu
     [not found]                           ` <DU2PR02MB10109B7AC39F995BFE266EF5396442@DU2PR02MB10109.eurprd02.prod.outlook.com>
2024-02-08  7:36                             ` Sv: " Arthur Miller
2024-02-12 21:39                       ` Stefan Monnier via Emacs development discussions.
2024-02-07 17:14                     ` Drew Adams
2024-02-07  5:32             ` Yuri Khan
2024-02-07 12:43               ` Arthur Miller
2024-02-07 17:41                 ` Alfred M. Szmidt
2024-02-07 18:36                   ` Arthur Miller
2024-02-07 19:12                     ` Alfred M. Szmidt
2024-02-07 21:20                       ` Arthur Miller
2024-02-06 17:29         ` [External] : " Drew Adams
2024-02-06 17:41           ` Alfred M. Szmidt
2024-02-06 17:50         ` Thierry Volpiatto
2024-02-06 19:04           ` Alfred M. Szmidt
2024-02-07 15:03           ` Barry Fishman
2024-02-07 17:22             ` [External] : " Drew Adams

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