From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Andrew Hyatt <ahyatt@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: pcase defuns
Date: Sun, 19 Dec 2021 12:23:59 -0500 [thread overview]
Message-ID: <jwvv8zka4zc.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <m2ilvldwll.fsf@andrews-mbp.lan> (Andrew Hyatt's message of "Sat, 18 Dec 2021 23:53:10 -0500")
> As a part of a personal project, I wrote a way to define functions in an
> equivalent way to pcases. For example:
>
> (pcase-defun mytest (a b _)
> "Match on 'a 'b with the third argument a wildcard"
> "a b match")
>
> (pcase-defun mytest (c ,var _)
> "Match on 'c binding VAR, with the third argument a wildcard"
> (format "c %s match" var) )
>
> (mytest 'a 'b 'c) -> "a b match"
> (mytest 'c 100 'c) -> "c 100 match"
>
> This is all accomplished by a few small but tricky macros and a hashtable
> that holds all the rules.
This kind of design crossed my mind a few times but I couldn't come up
with a way to give it a reasonable semantics and implementation.
Beside the issue of precedence/ordering already mentioned by Tassilo,
there's the issue of scoping and order/timing of macroexpansion. E.g.:
(let ((x 0))
(pcase-defun mytest (inc-x)
(setq x (1+ x)))
(pcase-defun mytest (get-x)
x))
(let ((y 0))
(pcase-defun mytest (inc-y)
(setq y (1+ y)))
(pcase-defun mytest (get-y)
y))
Does this work "right" with your code?
Or:
(eval-when-compile (require 'cl-lib))
(pcase-defun foo (..)
..
(cl-incf ..)
..)
is `cl-incf` properly macroexpanded during compilation of the file, or
is it delayed to when the file is loaded, at which point the `cl-incf`
macro may be undefined?
Stefan
next prev parent reply other threads:[~2021-12-19 17:23 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-19 4:53 pcase defuns Andrew Hyatt
2021-12-19 8:34 ` Tassilo Horn
2021-12-19 15:33 ` Andrew Hyatt
2021-12-19 17:16 ` Tassilo Horn
2021-12-19 19:05 ` Stefan Monnier
2021-12-20 5:56 ` Tassilo Horn
2021-12-22 14:07 ` LdBeth
2021-12-19 17:23 ` Stefan Monnier [this message]
2021-12-19 21:08 ` Andrew Hyatt
2021-12-21 4:15 ` Richard Stallman
2021-12-21 5:20 ` Andrew Hyatt
2021-12-22 4:18 ` Richard Stallman
2021-12-23 1:52 ` Andrew Hyatt
2021-12-24 4:13 ` Richard Stallman
2021-12-21 15:32 ` Stefan Monnier
2021-12-20 4:43 ` Richard Stallman
2021-12-23 2:30 ` Po Lu
2022-03-26 17:41 ` Andrew Hyatt
2022-03-27 9:31 ` Stefan Monnier
2022-03-27 18:17 ` Andrew Hyatt
2022-03-28 4:15 ` Richard Stallman
2022-03-30 1:28 ` Andrew Hyatt
2022-03-31 4:27 ` Richard Stallman
2022-04-17 22:09 ` Andrew Hyatt
2022-04-19 3:48 ` Richard Stallman
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