From: Joost Kremers <joost.m.kremers@gmail.com>
To: help-gnu-emacs@gnu.org
Subject: Re: Faking local dynamic function bindings
Date: 29 Jan 2014 09:05:23 GMT [thread overview]
Message-ID: <slrnlehh2j.6e2.joost.m.kremers@j.kremers4.news.arnhem.chello.nl> (raw)
In-Reply-To: mailman.13080.1390967480.10748.help-gnu-emacs@gnu.org
EN:SiS(9)
Stefan Monnier wrote:
>> (defun foo (sexpr)
>> (eval
>> `(cl-macrolet ((contains (regexp)
>> `(string-match ,regexp string)))
>> (sort (delq nil (mapcar #'(lambda (item)
>> (let ((string (assq item strings-alist)))
>> (when ,sexpr)
>> string))
>> items-alist))
>> 'string<))))
>
> IIUC, sexpr is only known very late (like much later than when you
> byte-compile this file).
Yes, you understand correctly.
> If that's the case, there's no avoiding `eval'.
This is the point where I hit myself over the head and say duh... That
should have been obvious, even to me.
> But you can move the eval closer to sexpr:
>
> (defun foo (sexpr)
> (sort (delq nil (mapcar #'(lambda (item)
> (let ((string (assq item strings-alist)))
> (when (eval
> `(cl-macrolet ((contains (regexp)
> `(string-match ,regexp ,string)))
> ,sexpr))
> string))
> items-alist))
> #'string<)))
This resembles an earlier version of my code, but AFAIU it has the
disadvantage that the local macro binding is created and destroyed every
time the anonymous function is executed, which I guess creates extra
overhead and makes the function slower. That's why I moved the
cl-macrolet outside the mapcar. (Though I haven't done any profiling and
the older version was fast enough not to be annoying...)
> And of course, you don't need `contains' to be a macro:
True, of course. However, I'm using a macro because in the actual code
one of the arguments of `contains` is an unquoted symbol. (That's an
unfortunate design decision I made years ago that has proven to be
completely pointless and impractical. I've been meaning to change it,
but haven't found the time to do so yet.)
Thanks,
Joost
--
Joost Kremers joostkremers@fastmail.fm
Selbst in die Unterwelt dringt durch Spalten Licht
next prev parent reply other threads:[~2014-01-29 9:05 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-29 2:04 Faking local dynamic function bindings Joost Kremers
2014-01-29 3:50 ` Stefan Monnier
[not found] ` <mailman.13080.1390967480.10748.help-gnu-emacs@gnu.org>
2014-01-29 9:05 ` Joost Kremers [this message]
2014-01-29 13:16 ` Stefan Monnier
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=slrnlehh2j.6e2.joost.m.kremers@j.kremers4.news.arnhem.chello.nl \
--to=joost.m.kremers@gmail.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.