Subject: bug#18555: 24.4.50; butlast and nbutlast doesn't handle improper lists

From: Leo Liu <[email-masked]>
Date: Thu, 25 Sep 2014 12:05:49 +0800

(nbutlast '(1 2 . 3))

throws an error due to `length' which can be fixed
by using safe-length instead.

  (butlast '(1 2 . 3))

still throws an error due to copy-sequence not taking
improper list.

What is the right thing to do?

Leo