GNU bug report logs - #67669
29.1; Drop text suggesting using `and' to replace `if'

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Message #61 received at 67669 <at> debbugs.gnu.org (full text, mbox):

From: Xiyue Deng <manphiz <at> gmail.com>
To: Sean Whitton <spwhitton <at> spwhitton.name>
Cc: 67669 <at> debbugs.gnu.org, Eli Zaretskii <eliz <at> gnu.org>
Subject: Re: bug#67669: 29.1; Drop text suggesting using `and' to replace `if'
Date: Fri, 08 Dec 2023 14:41:52 -0800

Sean Whitton <spwhitton <at> spwhitton.name> writes:

> Hello,
>
> On Thu 07 Dec 2023 at 09:49am -08, Xiyue Deng wrote:
>
>> Agreed on the point of being educational, and of course in the end
>> coding style is mostly a matter of personal preference.  However, I
>> would argue a bit that in such case we wouldn't need `if' or `when' at
>> all as both can be emulated by `and' and `or' if you are careful enough.
>> On the other hand, `if' and `when' should exist for a reason.  I quite
>> like this suggestion[1] that `if' and `when' are used to guard side
>> effects, whereas `and' and `or' are used for pure functions.
>> Interestingly the current example you quoted changed from using `and'
>> (as in the old version I quoted) to `if' probably based on this
>> reasoning.  Similarly I wouldn't suggest to replace `if' with `and' in
>> the original example around the text we are discussing:
>
> It's an old Lisp convention, not Emacs-specific, to use 'and' for return
> value and 'when' for side-effects, and not to use 'if' when there is no
> 'else' clause.

Ack.  Thanks for the historical tip!
-- 
Xiyue Deng

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