From: John Mastro <john.b.mastro@gmail.com>
To: emacs-devel@gnu.org
Subject: Re: if-let and when-let: parallel or sequential
Date: Mon, 11 Aug 2014 20:30:36 -0700 [thread overview]
Message-ID: <CAOj2CQRvkv5TsBXA8XCxVwTPS7=Cdc-_FM0j-FeuGy-JKU7zpw@mail.gmail.com> (raw)
In-Reply-To: <E1XH2YZ-0001HM-NB@fencepost.gnu.org>
Richard Stallman <rms@gnu.org> wrote:
> With several sequential bindings, the alternative is
>
> (let* ...bindings...
> (if ...))
>
> Thus, if-let saves just one level of nesting
> even if there are several bindings.
The current implementation in trunk is actually short-circuiting. So the
equivalent to:
(when-let ((a (foo))
(b (bar)))
b)
Would be:
(let ((a (foo)))
(when a
(let ((b (bar)))
b)))
And so on.
The only non-Clojure variant of these that I'm really familiar with is
Alexandria's[1]. It has both `-let' and `-let*' versions, allows
multiple bindings, and is not short circuiting. (I don't say this to
suggest we should mimic them, just to expose "where I'm coming from").
Anyway, I agree with Bozhidar that they'll be nice to have regardless of
the particulars, so I'll gracefully bow out :)
[1] http://common-lisp.net/gitweb?p=projects/alexandria/alexandria.git;a=blob;f=binding.lisp
--
john
next prev parent reply other threads:[~2014-08-12 3:30 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-10 2:44 if-let and when-let: parallel or sequential John Mastro
2014-08-10 15:22 ` Stefan Monnier
2014-08-11 12:01 ` Bozhidar Batsov
2014-08-11 14:42 ` Stefan Monnier
2014-08-11 16:40 ` Harald Hanche-Olsen
2014-08-11 17:49 ` Bozhidar Batsov
2014-08-11 20:55 ` Harald Hanche-Olsen
2014-08-12 2:43 ` Lars Magne Ingebrigtsen
2014-08-12 3:15 ` Richard Stallman
2014-08-12 3:30 ` John Mastro [this message]
2014-08-12 14:32 ` Elias Mårtenson
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