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From: "Alfred M. Szmidt" <ams@gnu.org>
To: Philip Kaludercic <philipk@posteo.net>
Cc: arthur.miller@live.com, emacs-devel@gnu.org
Subject: Re: cond* vs pcase
Date: Tue, 06 Feb 2024 11:17:05 -0500	[thread overview]
Message-ID: <E1rXO89-0003Ll-3B@fencepost.gnu.org> (raw)
In-Reply-To: <87il32iwmm.fsf@posteo.net> (message from Philip Kaludercic on Mon, 05 Feb 2024 18:39:13 +0000)


   "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/....

   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...

   >    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.



  parent reply	other threads:[~2024-02-06 16:17 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 [this message]
2024-02-06 16:35       ` [External] : " Drew Adams
2024-02-06 16:50       ` Philip Kaludercic
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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