From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Glenn Morris <rgm@gnu.org>
Cc: 12758@debbugs.gnu.org
Subject: bug#12758: letf no longer allows unbound variables
Date: Mon, 29 Oct 2012 09:46:56 -0400 [thread overview]
Message-ID: <jwv8vapcskw.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <cia9v5wwpn.fsf@fencepost.gnu.org> (Glenn Morris's message of "Mon, 29 Oct 2012 03:42:28 -0400")
> Evaluating this returns `99', and leaves `b' unbound. This behaviour is
> documented in cl.texi:
> In most cases, the @var{place} must have a well-defined value on
> entry to the @code{letf} form. The only exceptions are plain
> variables and calls to @code{symbol-value} and @code{symbol-function}.
> If the symbol is not bound on entry, it is simply made unbound by
> @code{makunbound} or @code{fmakunbound} on exit.
I think this was a bad idea, so it indeed doesn't work that way any
longer; more specifically:
- W.r.t symbol-function, this is still true for `letf' but not for
`cl-letf'.
- W.r.t symbol-value, this is not true any more neither of `letf' nor or
`cl-letf' (I could change that for letf but in the absence of
a bug-report pointing to pre-existing code that depends on this
behavior I'd rather not).
- For (letf ((b 4)) ...) this is still true, because it expands to (let
((b 4)) ...). But for (letf ((b)) ...) it isn't because that expands
to (let ((b b)) ...).
When `b' is a lexically-scoped variable, we really can't "fix" it
because lexical variables don't have a notion of "unbound".
Stefan
prev parent reply other threads:[~2012-10-29 13:46 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-29 7:42 bug#12758: letf no longer allows unbound variables Glenn Morris
2012-10-29 13:46 ` Stefan Monnier [this message]
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=jwv8vapcskw.fsf-monnier+emacs@gnu.org \
--to=monnier@iro.umontreal.ca \
--cc=12758@debbugs.gnu.org \
--cc=rgm@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.