From: "Basil L. Contovounesios" <contovob@tcd.ie>
To: Drew Adams <drew.adams@oracle.com>
Cc: Michael Heerdegen <michael_heerdegen@web.de>,
Barry Fishman <barry@ecubist.org>,
emacs-devel@gnu.org
Subject: Re: 7 logical-xor implementations in source tree
Date: Thu, 01 Aug 2019 01:05:40 +0300 [thread overview]
Message-ID: <87r265yi4r.fsf@tcd.ie> (raw)
In-Reply-To: <4de86e2c-18ab-4cf1-9a70-e43310234ad0@default> (Drew Adams's message of "Wed, 31 Jul 2019 14:38:01 -0700 (PDT)")
Drew Adams <drew.adams@oracle.com> writes:
> I don't understand what all the excitement
> about defining an `xor' (with whatever name)
> operator is about.
>
> Common Lisp, like Emacs Lisp, has a bit-wise
> xor operator. That makes sense - useful.
>
> And Common Lisp, like Emacs Lisp, does _not_
> have an xor operator for arbitrary Lisp values.
>
> https://www.cs.cmu.edu/Groups/AI/html/cltl/clm/node75.html
>
> Why is it important that Emacs Lisp have such
> an operator? (Answer: it's not - YAGNI.)
If YAGNI, why are there currently 7 copies of this function in the Emacs
sources?
No-one said it's vitally important; it's just a minor nice-to-have.
> Is it hard to understand (eq (not a) (not b))?
> Is evaluation of that inefficient? Is it too
> verbose?
>
> What's the motivation for all of this?
Same reason proper-list-p was added: reducing existing code duplication
and providing yet another convenience function for those that like it.
> My vote's against adding any such operator.
--
Basil
next prev parent reply other threads:[~2019-07-31 22:05 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-22 18:48 7 logical-xor implementations in source tree Oleh Krehel
2019-07-22 21:47 ` Basil L. Contovounesios
2019-07-24 22:17 ` Basil L. Contovounesios
2019-07-24 23:15 ` Stefan Monnier
2019-07-24 23:44 ` Basil L. Contovounesios
2019-07-25 12:07 ` Mattias Engdegård
2019-07-25 17:28 ` Paul Eggert
2019-07-25 17:46 ` Mattias Engdegård
2019-07-28 7:09 ` Philippe Schnoebelen
2019-07-28 8:04 ` Alan Mackenzie
2019-07-28 19:43 ` Marcin Borkowski
2019-07-30 9:36 ` Alan Mackenzie
2019-07-30 10:57 ` Philippe Schnoebelen
2019-07-30 11:28 ` Andy Moreton
2019-07-30 12:34 ` Stefan Monnier
2019-07-30 14:25 ` Barry Fishman
2019-07-31 3:16 ` Richard Stallman
2019-07-31 15:20 ` Barry Fishman
2019-07-31 15:42 ` Stefan Monnier
2019-07-31 20:22 ` Basil L. Contovounesios
2019-07-31 21:15 ` Michael Heerdegen
2019-07-31 22:28 ` Mattias Engdegård
2019-07-31 23:39 ` Basil L. Contovounesios
2019-08-02 10:29 ` Mattias Engdegård
2019-08-02 10:59 ` Basil L. Contovounesios
2019-08-06 11:58 ` Mattias Engdegård
2019-07-31 20:31 ` Michael Heerdegen
2019-07-31 21:38 ` Drew Adams
2019-07-31 22:03 ` Drew Adams
2019-07-31 22:05 ` Basil L. Contovounesios [this message]
2019-07-31 23:20 ` Drew Adams
2019-08-01 0:09 ` Basil L. Contovounesios
2019-07-31 17:12 ` Marcin Borkowski
2019-07-23 8:39 ` Andy Moreton
2019-07-23 9:08 ` Basil L. Contovounesios
2019-07-23 9:14 ` Mattias Engdegård
2019-07-23 10:26 ` Andy Moreton
2019-07-23 10:40 ` Andreas Schwab
2019-07-23 12:11 ` Andy Moreton
2019-07-23 13:20 ` Basil L. Contovounesios
2019-07-23 13:54 ` Andy Moreton
2019-07-24 22:21 ` Basil L. Contovounesios
2019-07-23 10:44 ` Basil L. Contovounesios
2019-07-23 11:01 ` Yuri Khan
2019-07-25 21:46 ` Juri Linkov
2019-07-23 11:24 ` Noam Postavsky
2019-07-23 12:38 ` Stefan Monnier
2019-07-23 16:41 ` Mattias Engdegård
2019-07-23 17:12 ` Eli Zaretskii
2019-07-23 17:48 ` Paul Eggert
2019-07-23 19:45 ` Stefan Monnier
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