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From: Drew Adams <drew.adams@oracle.com>
To: Michael Heerdegen <michael_heerdegen@web.de>,
	Barry Fishman <barry@ecubist.org>
Cc: emacs-devel@gnu.org
Subject: RE: 7 logical-xor implementations in source tree
Date: Wed, 31 Jul 2019 15:03:02 -0700 (PDT)	[thread overview]
Message-ID: <f6b19ed9-464b-41e1-877a-4317a75d8da0@default> (raw)
In-Reply-To: <4de86e2c-18ab-4cf1-9a70-e43310234ad0@default>

> Is it hard to understand (eq (not a) (not b))?

Well, someone off list pointed out that that is
(not (xor a b)); it is not (xor a b).  Yes, of
course.

I thought it'd be enough to speak to the general
thing under discussion, for which opposite-value
names such as "equiv", "iff", and `<=>' were
proposed.

But to be more pedantic/correct, is it hard to 
understand (not (eq (not a) (not b)))?
Or if you prefer, (eq (not a) (not (not b)))?

Is lack of an `xor' (or an `equiv') operator
a problem in practice?  How often have you felt
the need for it, really?

Why do you think Emacs Lisp, which was by design 
smaller than Common Lisp, needs such a function,
but Common Lisp does not?  What's the special
need we have for this?



  reply	other threads:[~2019-07-31 22:03 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 [this message]
2019-07-31 22:05                                   ` Basil L. Contovounesios
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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