From: Tino Calancha <tino.calancha@gmail.com>
To: Philipp Stephani <p.stephani2@gmail.com>
Cc: 25154@debbugs.gnu.org, agrambot@gmail.com, tino.calancha@gmail.com
Subject: bug#25154: 25.1; Bindings in cl-letf are in reverse order
Date: Fri, 23 Dec 2016 21:46:39 +0900 [thread overview]
Message-ID: <8760ma4xu8.fsf@gmail.com> (raw)
In-Reply-To: <CAArVCkS=F6ZGwSBgum-ST31t_0+nY9oRAkqFofSb4FHFXYdCZA@mail.gmail.com> (Philipp Stephani's message of "Fri, 23 Dec 2016 12:17:54 +0000")
Philipp Stephani <p.stephani2@gmail.com> writes:
> I agree, patches to that effect are welcome. (AFAICT, the manual
> tries to say that already, but the wording could be more explicit.)
>
> OK, I've attached a patch that hopefully clarifies this a bit.
>
> From 42d7450c41d69a713eb8f9492cc169e8c2bc15ca Mon Sep 17 00:00:00 2001
> From: Philipp Stephani <phst@google.com>
> Date: Fri, 23 Dec 2016 13:14:55 +0100
> Subject: [PATCH] Document that variable binding order is unspecified
>
> * doc/lispref/variables.texi (Local Variables):
> * cl.texi (Modify Macros): Document that assignment order in 'let' and
> 'cl-letf' is unspecified.
> ---
> doc/lispref/variables.texi | 12 ++++++++++++
> doc/misc/cl.texi | 5 +++++
> 2 files changed, 17 insertions(+)
>
> diff --git a/doc/lispref/variables.texi b/doc/lispref/variables.texi
> index a2d64815d9..e2c8c542ab 100644
> --- a/doc/lispref/variables.texi
> +++ b/doc/lispref/variables.texi
> @@ -221,6 +221,18 @@ Local Variables
> @result{} (1 2)
> @end group
> @end example
> +
> +On the other hand, the order of @emph{assignments} is unspecified: in
> +the following example, either 1 or 2 might be printed.
> +
> +@example
> +(let ((x 1)
> + (x 2))
> + (print x))
> +@end example
> +
> +Therefore, avoid binding a variable more than once in a single
> +@code{let} form.
> @end defspec
>
> @defspec let* (bindings@dots{}) forms@dots{}
> diff --git a/doc/misc/cl.texi b/doc/misc/cl.texi
> index c62fa727c1..aa047e2122 100644
> --- a/doc/misc/cl.texi
> +++ b/doc/misc/cl.texi
> @@ -1179,6 +1179,11 @@ Modify Macros
> as @code{setf} places; each will accept either an integer or a
> marker as the stored value.)
>
> +Like in the case of @code{let}, the @var{value} forms are evaluated in
> +the order they appear, but the order of assignments is unspecified.
> +Therefore, avoid assigning to the same @var{place} more than once in a
> +single @code{cl-letf} form.
> +
> Since generalized variables look like lists, @code{let}'s shorthand
> of using @samp{foo} for @samp{(foo nil)} as a @var{binding} would
> be ambiguous in @code{cl-letf} and is not allowed.
It looks good to me. Thank you.
Tino
next prev parent reply other threads:[~2016-12-23 12:46 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-09 23:36 bug#25154: 25.1; Bindings in cl-letf are in reverse order Alex
2016-12-10 4:29 ` Alex
2016-12-10 7:22 ` Eli Zaretskii
2016-12-10 7:43 ` Tino Calancha
2016-12-10 13:41 ` Philipp Stephani
2016-12-10 14:01 ` Tino Calancha
2016-12-10 14:09 ` Eli Zaretskii
2016-12-23 12:17 ` Philipp Stephani
2016-12-23 12:46 ` Tino Calancha [this message]
2016-12-23 13:53 ` Eli Zaretskii
2016-12-23 16:30 ` Philipp Stephani
2016-12-10 18:05 ` Alex
2016-12-10 18:14 ` npostavs
2016-12-10 19:41 ` Alex
2016-12-10 18:27 ` Eli Zaretskii
2016-12-10 19:52 ` Alex
2016-12-11 3:11 ` Tino Calancha
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