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From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Richard Stallman <rms@gnu.org>
Cc: emacs-devel@gnu.org
Subject: Re: Installing cond* in core
Date: Fri, 02 Feb 2024 08:17:25 -0500	[thread overview]
Message-ID: <jwvzfwj57to.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <E1rVkOa-0008Ax-Jn@fencepost.gnu.org> (Richard Stallman's message of "Thu, 01 Feb 2024 22:39:16 -0500")

>   > I think the question is rather: why should we have two equivalent and
>   > almost identical matching syntaxes and implementations?
> That is the easiest way to make cond* function.

Only if you consider "easiest" at each small incremental step.
The overall cost of what you've done is already much higher :-)

> I do not understand the pcase code for implementing pattern matching,

You don't need to understand it.

> A priori, I suspect it won't fit.  cond*-subpat, which does this job
> in cond*, passes data up and down the recursion.  I can't tell whether
> pcase does something comparable.  Also, cond*-subpat does not generate
> the overall structure of a clause -- its caller, cond*-match, does
> that.

Throw away cond*-subpat.  Just rewrite

    (cond*
     ((match* PAT FORM) THEN)
     . ELSE)

into something like

    (pcase FORM
      (PAT THEN)
      (_ (cond* . ELSE)))

And presumably for

    (cond*
     ((match* PAT FORM))
     . REST)

you'd rewrite it to

    (pcase-let ((PATH FORM))
      (cond* . REST))

No need to look inside or understand `pcase.el` at all!



        Stefan




  reply	other threads:[~2024-02-02 13:17 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-01-27 21:36 Installing cond* in core Stefan Kangas
2024-01-27 23:33 ` Alan Mackenzie
2024-01-28  0:26   ` Stefan Kangas
2024-01-28  2:43     ` Po Lu
2024-01-28  6:46       ` Eli Zaretskii
2024-01-28  7:21         ` Po Lu
2024-01-28  7:32           ` Eli Zaretskii
2024-01-28  6:14     ` Eli Zaretskii
2024-01-28 15:58     ` Alan Mackenzie
2024-01-28  6:09   ` Eli Zaretskii
2024-01-28 12:38     ` Alan Mackenzie
2024-01-28 13:02       ` Dmitry Gutov
2024-01-28 13:38         ` Alan Mackenzie
2024-01-28 13:48           ` Dmitry Gutov
2024-01-28 14:32             ` Alan Mackenzie
2024-01-28 16:54               ` Dmitry Gutov
2024-01-28 19:14                 ` Alan Mackenzie
2024-01-28 19:26                   ` Eli Zaretskii
2024-01-28 20:43                   ` Dmitry Gutov
2024-01-30  3:56                 ` Richard Stallman
2024-01-28 13:19       ` Emanuel Berg
2024-01-28 14:18       ` Eli Zaretskii
2024-01-28 15:26         ` Alan Mackenzie
2024-01-28 15:40           ` Eli Zaretskii
2024-01-30  3:57             ` Richard Stallman
2024-01-28  4:28 ` Stefan Monnier via Emacs development discussions.
2024-01-30  3:58   ` Richard Stallman
2024-01-30 14:33     ` Stefan Monnier
2024-02-02  3:39       ` Richard Stallman
2024-02-02 13:17         ` Stefan Monnier [this message]
2024-02-02 15:24           ` Alan Mackenzie
2024-02-02 18:50             ` Stefan Monnier
2024-02-04  4:47               ` Richard Stallman
2024-02-04 14:12                 ` Stefan Monnier
2024-02-06  3:49                   ` Richard Stallman
2024-02-05  3:33           ` Richard Stallman
2024-02-05 12:39             ` Stefan Monnier
2024-03-13  2:27               ` Richard Stallman
2024-03-13  3:05                 ` Stefan Monnier
2024-03-16  1:45                   ` Richard Stallman
2024-03-16 16:15                     ` Stefan Monnier
2024-03-18  2:42                       ` Richard Stallman
2024-03-18  3:06                         ` Stefan Monnier
2024-03-19  9:19                           ` Peter Hull
2024-03-20 22:40                           ` Richard Stallman
2024-03-20 22:54                             ` Stefan Monnier
2024-01-28 14:28 ` Emanuel Berg
2024-01-30  3:58 ` Richard Stallman
2024-01-30 13:04   ` Eli Zaretskii
2024-03-16 20:53 ` Lynn Winebarger
2024-03-18  2:41   ` Richard Stallman
2024-03-19 19:48     ` Lynn Winebarger

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