From: pjb@informatimago.com (Pascal J. Bourguignon)
To: help-gnu-emacs@gnu.org
Subject: Re: case or cond
Date: Sun, 11 Oct 2009 19:22:17 +0200 [thread overview]
Message-ID: <87skdprgl2.fsf@galatea.local> (raw)
In-Reply-To: a5bd35f4-8293-4cc5-a88b-3daf88d7389e@g31g2000yqc.googlegroups.com
Nordlöw <per.nordlow@gmail.com> writes:
> Is case more inefficient than cond?
>
> Does it depend on what kinds of objects that are compared?
Notice that case documentation says that:
Key values are compared by `eql'.
So:
(case expr
(v1 e1)
((v21 ... v2p) e2)
...
(otherwise eo))
is equivalent to:
(let ((e expr))
(cond
((eql e v1) e1)
((memq e '(v21 ... v2p)) e2)
...
(t eo)))
If your cond is not of that form, then it's hardly comparable to case.
On the other hand if it is, then indeed, case might be faster, because
it isn't necessarily implemented as a sequence of tests like cond.
--
__Pascal Bourguignon__
next prev parent reply other threads:[~2009-10-11 17:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-10 10:03 case or cond Nordlöw
2009-10-11 17:22 ` Pascal J. Bourguignon [this message]
-- strict thread matches above, loose matches on Subject: below --
2009-10-10 10:03 Nordlöw
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87skdprgl2.fsf@galatea.local \
--to=pjb@informatimago.com \
--cc=help-gnu-emacs@gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this external index
https://git.savannah.gnu.org/cgit/emacs.git
https://git.savannah.gnu.org/cgit/emacs/org-mode.git
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.