From: Leo <sdl.web@gmail.com>
To: emacs-devel@gnu.org
Subject: Re: Common Lisp like feature expressions (was: How and when to use GCPRO?)
Date: Mon, 27 Dec 2010 19:57:55 +0000 [thread overview]
Message-ID: <m18vzbgf98.fsf@cam.ac.uk> (raw)
In-Reply-To: m2pqsn9fbm.fsf@whitebox.home
On 2010-12-27 19:38 +0000, Andreas Schwab wrote:
> Leo <sdl.web@gmail.com> writes:
>
>> +(defun eval-feature-expression (form)
>> + (cond
>> + ((atom form) (featurep form nil))
>> + ;; ensure form is a proper list
>> + ((condition-case nil
>> + (and (length form) nil)
>
> Nice quadratic behaviour.
>
> Andreas.
How about something like this:
(defun eval-feature-expression (form)
(cond
((atom form) (featurep form nil))
((eq (car form) 'not)
(not (eval-feature-expression (cadr form))))
((eq (car form) 'and)
(if (not (cdr form))
t
(and (eval-feature-expression (cadr form))
(eval-feature-expression (cons 'and (cddr form))))))
((eq (car form) 'or)
(if (not (cdr form))
nil
(or (eval-feature-expression (cadr form))
(eval-feature-expression (cons 'or (cddr form))))))
(t (error "Invalid feature expression: %s" form))))
Leo
next prev parent reply other threads:[~2010-12-27 19:57 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-27 9:21 How and when to use GCPRO? Leo
2010-12-27 10:15 ` Andreas Schwab
2010-12-27 10:38 ` Leo
2010-12-27 11:17 ` Andreas Schwab
2010-12-27 16:00 ` Stefan Monnier
2010-12-27 17:51 ` Andreas Schwab
2010-12-28 1:01 ` Stefan Monnier
2010-12-28 1:33 ` Daniel Colascione
2010-12-28 2:17 ` Stefan Monnier
2010-12-28 3:37 ` Daniel Colascione
2010-12-28 4:15 ` Stefan Monnier
2010-12-28 4:36 ` Conservative scanning (was: Re: How and when to use GCPRO?) Daniel Colascione
2010-12-28 17:07 ` How and when to use GCPRO? Richard Stallman
2010-12-27 19:15 ` Leo
2010-12-27 19:26 ` Common Lisp like feature expressions (was: How and when to use GCPRO?) Leo
2010-12-27 19:38 ` Andreas Schwab
2010-12-27 19:57 ` Leo [this message]
2010-12-28 1:01 ` Common Lisp like feature expressions Stefan Monnier
2010-12-28 15:26 ` Leo
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=m18vzbgf98.fsf@cam.ac.uk \
--to=sdl.web@gmail.com \
--cc=emacs-devel@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.