From: Stefan Monnier via Users list for the GNU Emacs text editor <help-gnu-emacs@gnu.org>
To: help-gnu-emacs@gnu.org
Subject: Re: Generic functions: Specializers like `or' or `memq'?
Date: Sat, 06 Nov 2021 19:36:14 -0400 [thread overview]
Message-ID: <jwvpmrcamns.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: 878ry0nce8.fsf@web.de
>> [ `cl-generic.el` solves this problem by forcing the generalizer to
>> come with a priority (a number), which makes the ordering "trivial"
>> for `cl-generic.el` but it can be hard to choose the right priority
>> to use when defining a new specializer/generalizer. ]
>
> I don't see this. How would an `or' or `memql' specializer be different
> from implementing the method several times for each alternative using
> the same body?
You need to specify the priority of things like
(or (eql 4) integer)
and
(or (eql 4) (eql 5))
and
(or (eql 4) (eql "hello"))
The first wants to have lower priority than `integer`, the second should
have higher priority than `integer`, as for the third ... well ...
It's easier to move the code to a separate function and use individual
`cl-defmethod`s for each case, all of them implemented by calling that
separate function.
Stefan
next prev parent reply other threads:[~2021-11-06 23:36 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-03 17:17 Generic functions: Specializers like `or' or `memq'? Michael Heerdegen
2021-11-03 18:21 ` Philip Kaludercic
2021-11-03 21:10 ` Michael Heerdegen
2021-11-03 21:32 ` Eric Abrahamsen
2021-11-03 23:19 ` Michael Heerdegen
2021-11-03 23:38 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-11-04 0:26 ` Michael Heerdegen
2021-11-04 1:31 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-11-04 2:34 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-11-04 4:01 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-11-06 22:32 ` Michael Heerdegen
2021-11-06 23:36 ` Stefan Monnier via Users list for the GNU Emacs text editor [this message]
2021-11-07 1:48 ` Michael Heerdegen
2021-11-21 19:43 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-11-23 8:16 ` Michael Heerdegen
-- strict thread matches above, loose matches on Subject: below --
2021-11-04 17:31 Eric Abrahamsen
2021-11-05 21:17 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-11-05 21:36 ` Emanuel Berg via Users list for the GNU Emacs text editor
2021-11-06 23:29 ` Stefan Monnier via Users list for the GNU Emacs text editor
2021-11-06 23:52 ` Emanuel Berg via Users list for the GNU Emacs text editor
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