GNU bug report logs - #24875
26.0.50; In Dotted Pair Notation, the read function returns CDR if CAR is absent

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Package: emacs;

Reported by: Chunyang Xu <mail <at> xuchunyang.me>

Date: Fri, 4 Nov 2016 15:40:03 UTC

Severity: minor

Tags: moreinfo

Found in version 26.0.50

Fixed in version 28.1

Done: Lars Ingebrigtsen <larsi <at> gnus.org>

Bug is archived. No further changes may be made.

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Chunyang Xu <mail <at> xuchunyang.me>
To: bug-gnu-emacs <at> gnu.org
Subject: 26.0.50;
 In Dotted Pair Notation, the read function returns CDR if CAR is
 absent
Date: Fri, 04 Nov 2016 21:36:38 +0800

For example, I eval this in the *scratch* buffer:

(read "( . 123)")
     ⇒ 123

(read "(1 . ( . (3 . nil)))")
     ⇒ (1 3)

I can't find explanation about this behavior in elisp manual. Is it
expected?

According to an answer [1] by wasamasa on Emacs StackExchange,
Guile behaves the same, but other Lisp interpreters (csi, pil and sbcl)
and MIT-Scheme don't permit reading this.


[1] http://emacs.stackexchange.com/a/28410/3889
This bug report was last modified 4 years and 33 days ago.

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