From: Michael Heerdegen <michael_heerdegen@web.de>
To: Noam Postavsky <npostavs@users.sourceforge.net>
Cc: Mark Oteiza <mvoteiza@udel.edu>, 28254@debbugs.gnu.org
Subject: bug#28254: 26.0.50; SRFI-2 and-let*
Date: Sun, 03 Sep 2017 19:48:13 +0200 [thread overview]
Message-ID: <87vakzwu5e.fsf@drachen> (raw)
In-Reply-To: <CAM-tV-8w7YaUKcjcEC5OYB=5OE7Jx8hYkT1LxSoKX704Q99_Qw@mail.gmail.com> (Noam Postavsky's message of "Sat, 2 Sep 2017 14:41:03 -0400")
Noam Postavsky <npostavs@users.sourceforge.net> writes:
> On Sat, Sep 2, 2017 at 9:36 AM, Mark Oteiza <mvoteiza@udel.edu> wrote:
> > On 02/09/17 at 07:25am, Michael Heerdegen wrote:
> >>
> >> Isn't there a problem with EXPR being a symbol S, which already has a
> >> different meaning (bind S to nil)? Though, this seems barely
> >> useful to
> >> me. Anyway, introducing (EXPR) would thus be backward incompatible.
>
> What would be the point of binding S to nil? In the foo-let macros
> that would be equivalent to just putting nil (if non-list EXPRs are
> supported), no?
Eh hmm - yes, I think so. It isn't useful.
> I think I'd be okay with dropping support for the S = (S nil) thing in
> foo-let macros, so that all of the above would give (void-variable x).
> Although perhaps the incompatibility with plain let would be annoying?
> To be honest I hardly ever make use of S = (S nil) in plain let either
> so it wouldn't hit me at all.
I think the main use case is to declare a local variable when you don't
care about the init value. In the case of if-let, S = (S nil) is not
useful, since you can't use that binding neither in the "then" clause
(because it won't be executed) nor in the "else" clauses (which ignore
all bindings).
Even if an `if-let' form is the result of a macro expansion, the S = (S
nil) case isn't of any value. So I see no reasons to not drop support
for it.
Michael.
next prev parent reply other threads:[~2017-09-03 17:48 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-27 20:11 bug#28254: 26.0.50; SRFI-2 and-let* Mark Oteiza
2017-09-01 2:55 ` npostavs
2017-09-02 2:10 ` Mark Oteiza
2017-09-02 3:05 ` npostavs
2017-09-02 4:14 ` Mark Oteiza
2017-09-02 5:25 ` Michael Heerdegen
2017-09-02 13:36 ` Mark Oteiza
2017-09-02 18:41 ` Noam Postavsky
2017-09-03 17:48 ` Michael Heerdegen [this message]
2017-09-03 22:39 ` Mark Oteiza
2017-09-04 0:48 ` Mark Oteiza
2017-09-04 14:12 ` Michael Heerdegen
2017-09-05 3:47 ` Mark Oteiza
2017-09-05 15:04 ` Michael Heerdegen
2017-09-06 12:12 ` Michael Heerdegen
2017-09-06 13:06 ` Mark Oteiza
2017-09-06 19:04 ` Michael Heerdegen
2017-09-04 1:13 ` Mark Oteiza
2017-09-05 3:55 ` Mark Oteiza
2017-09-09 0:33 ` Mark Oteiza
2017-09-12 12:39 ` Michael Heerdegen
2017-09-12 13:09 ` Mark Oteiza
2017-09-12 18:44 ` Michael Heerdegen
2017-09-12 20:21 ` Mark Oteiza
2017-09-13 10:16 ` Michael Heerdegen
2017-09-13 11:48 ` Mark Oteiza
2017-09-13 16:46 ` Michael Heerdegen
2017-09-13 16:49 ` Mark Oteiza
2017-09-13 17:05 ` Michael Heerdegen
2017-09-13 17:28 ` Mark Oteiza
2017-09-13 17:49 ` Michael Heerdegen
2017-09-12 12:13 ` Michael Heerdegen
2017-09-12 14:29 ` Mark Oteiza
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