From: Drew Adams <drew.adams@oracle.com>
To: Kaushal Modi <kaushal.modi@gmail.com>,
Help Gnu Emacs mailing list <help-gnu-emacs@gnu.org>
Subject: RE: What's the canonical way to check "alistp"?
Date: Thu, 1 Mar 2018 09:06:21 -0800 (PST) [thread overview]
Message-ID: <5392b397-4974-42cd-9328-161ba7f72f2f@default> (raw)
In-Reply-To: <CAFyQvY1cVaUK03zje1Pxor3H4_hS7-amHg=uxKxX3=Q8GWFuBA@mail.gmail.com>
> What's the best way to check if every element in a list is also a list?
Also a _list_ or also a cons? Do you want (alistp '(()))
to return true? I'm guessing no.
(defun alistp (xs)
"Return non-nil iff XS is a list and each element is a cons."
(and (listp xs)
(catch 'alistp
(dolist (x xs) (unless (consp x) (throw 'alistp nil)))
t)))
(The code should not bother to check each element if it
finds one that is not a cons.)
next prev parent reply other threads:[~2018-03-01 17:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-01 15:21 What's the canonical way to check "alistp"? Kaushal Modi
2018-03-01 15:29 ` Kaushal Modi
2018-03-01 15:33 ` Dmitry Gutov
2018-03-01 16:36 ` Kaushal Modi
2018-03-01 17:06 ` Drew Adams [this message]
[not found] ` <mailman.9955.1519924176.27995.help-gnu-emacs@gnu.org>
2018-03-05 19:17 ` Robert L.
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