From: Yuri Khan <yurivkhan@gmail.com>
To: galex-713@galex-713.eu
Cc: Stefan Monnier <monnier@iro.umontreal.ca>,
Emacs developers <emacs-devel@gnu.org>
Subject: Re: Why is there no `until' in elisp?
Date: Wed, 17 Oct 2018 16:46:08 +0700 [thread overview]
Message-ID: <CAP_d_8V6EgbbTvzeNjKTJEHXW24yy-hUu==qCuTqR27zMpwXjQ@mail.gmail.com> (raw)
In-Reply-To: <87lg6xgc58.fsf@portable.galex-713.eu>
On Wed, Oct 17, 2018 at 4:23 PM Garreau, Alexandre
<galex-713@galex-713.eu> wrote:
>
> Something such as the C “do” construct might overcomplicate the
> language, while I think normal `while' and `until' are not only simpler
> but also superior: with those you have the case of 0 loops, in which
> basically works as a when.
The post-condition loop enables the “at-least-once” case, which is
also occasionally useful, e.g.: Attempt an API call until it succeeds.
> > However, in many languages that have an ‘until’ loop as a language
> > construct, it is a post-condition loop. The body is executed first,
> > then the condition is evaluated.
>
> Which languages? I looked again in bash to be sure, and bash doesn’t do
> that.
+ Well, you mentioned the C ‘do’/‘while’, for one; it is a
continuation post-condition loop. C++, Java, PHP, Javascript and many
other languages inherited that.
+ Pascal has ‘repeat’/‘until’ (a termination post-condition loop), and
it was my first association for the name ‘until’.
− Bash’s ‘until’/‘do’/‘done’ is a termination pre-condition loop, you’re right.
+ In Perl, both ‘while’ (continuation) and ‘until’ (termination) can
be used as pre-conditions and post-conditions.
next prev parent reply other threads:[~2018-10-17 9:46 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-16 17:42 Why is there no `until' in elisp? Garreau, Alexandre
2018-10-16 19:16 ` Eric Abrahamsen
2018-10-16 19:31 ` Garreau, Alexandre
2018-10-16 20:23 ` Eric Abrahamsen
2018-10-16 23:00 ` Garreau, Alexandre
2018-10-19 15:28 ` Stefan Monnier
2018-10-16 21:28 ` Stefan Monnier
2018-10-17 0:12 ` Garreau, Alexandre
2018-10-17 2:04 ` Stefan Monnier
2018-10-17 9:14 ` Garreau, Alexandre
2018-10-17 15:06 ` Stefan Monnier
2018-10-17 16:51 ` Garreau, Alexandre
2018-10-19 15:34 ` Stefan Monnier
2018-10-19 18:08 ` Garreau, Alexandre
2018-10-17 8:04 ` Yuri Khan
2018-10-17 9:23 ` Garreau, Alexandre
2018-10-17 9:46 ` Yuri Khan [this message]
2018-10-17 11:06 ` Garreau, Alexandre
2018-10-17 17:50 ` Paul Eggert
2018-10-17 21:15 ` Garreau, Alexandre
2018-10-17 21:35 ` Paul Eggert
2018-10-17 21:49 ` Garreau, Alexandre
2018-10-17 22:33 ` Paul Eggert
2018-10-17 22:54 ` Garreau, Alexandre
2018-10-17 12:41 ` Elias Mårtenson
2018-10-17 15:03 ` Stefan Monnier
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