From: Noam Postavsky <npostavs@gmail.com>
To: Vladimir Sedach <vas@oneofus.la>
Cc: Michael Heerdegen <michael_heerdegen@web.de>,
Juanma Barranquero <lekktu@gmail.com>,
Emacs developers <emacs-devel@gnu.org>,
Stefan Kangas <stefankangas@gmail.com>,
Drew Adams <drew.adams@oracle.com>,
Stefan Monnier <monnier@iro.umontreal.ca>
Subject: Re: master 8f0f851: * lisp/autoarg.el: Use lexical binding.
Date: Wed, 29 Apr 2020 11:05:20 -0400 [thread overview]
Message-ID: <CAM-tV-8LD+HLh3XU82pVyEEvqTLWYXiiLs5R1p29zjYOw_LPEQ@mail.gmail.com> (raw)
In-Reply-To: <87imhj2faz.fsf@t510.orion.oneofus.la>
On Tue, 28 Apr 2020 at 22:35, Vladimir Sedach <vas@oneofus.la> wrote:
> Drew Adams <drew.adams@oracle.com> writes:
> > Why was RESULT deprecated?
>
> That is indeed bizarre. Why break existing Elisp code? David
> Touretzky provides lots of examples of how to use RESULT with DOTIMES
> and DOLIST in _Common Lisp: A Gentle Introduction_.
I think it's useful to look at a couple of concrete examples from
there. I found it at <https://www.cs.cmu.edu/~dst/LispBook/book.pdf>.
There is this kind of usage (page 345):
(defun it-intersection (x y)
(let ((result-set nil))
(dolist (element x result-set)
(when (member element y)
(push element result-set)))))
The argument for deprecating the RESULT param is mainly because code
like this is (arguably) clearer when written
(defun it-intersection (x y)
(let ((result-set nil))
(dolist (element x)
(when (member element y)
(push element result-set)))
result-set))
Because it's easier to quickly pick out what the return value is.
Obviously it's a matter of taste to some degree though.
There's another kind of usage that isn't as easily replaced (page 343):
(defun check-all-odd (list-of-numbers)
(dolist (e list-of-numbers t)
(format t "~&Checking ~S..." e)
(if (not (oddp e)) (return nil))))
But this relies on dolist establishing a block that be used with
return. So in elisp, this should be done with cl-dolist which I
believe everyone agrees will always support the RESULT argument.
next prev parent reply other threads:[~2020-04-29 15:05 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200419004503.26161.91884@vcs0.savannah.gnu.org>
[not found] ` <20200419004504.C65772049B@vcs0.savannah.gnu.org>
2020-04-19 6:18 ` master 8f0f851: * lisp/autoarg.el: Use lexical binding Juanma Barranquero
2020-04-20 5:10 ` Stefan Kangas
2020-04-20 5:34 ` Michael Heerdegen
2020-04-20 11:06 ` Noam Postavsky
2020-04-20 13:52 ` Stefan Monnier
2020-04-20 14:55 ` Drew Adams
2020-04-20 16:32 ` Stefan Monnier
2020-04-28 2:14 ` Michael Heerdegen
2020-04-28 2:59 ` Strange compiler warning in `dotimes' (was: master 8f0f851: * lisp/autoarg.el: Use lexical binding.) Michael Heerdegen
2020-04-28 15:32 ` master 8f0f851: * lisp/autoarg.el: Use lexical binding Drew Adams
2020-04-29 0:53 ` Michael Heerdegen
2020-04-29 0:59 ` Drew Adams
2020-04-29 1:13 ` Michael Heerdegen
2020-04-29 1:23 ` Drew Adams
2020-04-29 2:31 ` Vladimir Sedach
2020-04-29 3:58 ` Michael Heerdegen
2020-04-29 4:21 ` Stefan Monnier
2020-04-29 18:33 ` Vladimir Sedach
2020-04-29 4:02 ` Stefan Monnier
2020-04-29 15:05 ` Noam Postavsky [this message]
2020-04-30 2:26 ` Richard Stallman
2020-05-16 3:21 ` Michael Heerdegen
2020-04-29 3:53 ` Stefan Monnier
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