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From: "Stephen J. Turnbull" <stephen@xemacs.org>
To: Tom Tromey <tromey@redhat.com>
Cc: Bob Rogers <rogers-emacs@rgrjr.dyndns.org>,
	"Lennart Borgman \(gmail\)" <lennart.borgman@gmail.com>,
	Emacs Devel <emacs-devel@gnu.org>
Subject: Re: To be a list or not
Date: Sun, 30 Dec 2007 09:54:41 +0900	[thread overview]
Message-ID: <87abnt6lym.fsf@uwakimon.sk.tsukuba.ac.jp> (raw)
In-Reply-To: <m3abntf7ea.fsf@fleche.redhat.com>

Tom Tromey writes:
 > >>>>> "Stephen" == Stephen J Turnbull <stephen@xemacs.org> writes:
 > 
 > Stephen> But please call it `true-list-p', which is the name of the
 > Stephen> similar XEmacs built-in.
 > 
 > Here's one stab at it.  This is basically lifted from safe-length.

Looks very familiar.

XEmacs implements one change you might think about.  Specifically, it
delays starting the tortoise until the length is "long enough to
suspect circularity".  I don't know if the value chosen was tuned or
not.  As I understand it, this makes the function slightly faster for
shorter lists, slightly slows down longer true lists, and might double
the detection time for cyclical lists.

Looks like a win to me, but YMMV.

  parent reply	other threads:[~2007-12-30  0:54 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-28 21:20 To be a list or not Lennart Borgman (gmail)
2007-12-28 21:40 ` Eric Hanchrow
2007-12-28 21:47 ` Nick Roberts
2007-12-28 23:05   ` Lennart Borgman (gmail)
2007-12-28 23:45     ` Nick Roberts
2007-12-29  0:18       ` Lennart Borgman (gmail)
2007-12-29  3:35         ` Bob Rogers
2007-12-29 21:11           ` Stephen J. Turnbull
2007-12-29 22:40             ` Miles Bader
2007-12-29 22:44             ` Tom Tromey
2007-12-29 23:22               ` Andreas Schwab
2007-12-31 16:38                 ` Tom Tromey
2007-12-31 17:13                   ` Andreas Schwab
2007-12-30  0:54               ` Stephen J. Turnbull [this message]
2007-12-30  3:52                 ` Bob Rogers
2007-12-30  1:37               ` Richard Stallman
2007-12-29 17:49     ` Richard Stallman
2007-12-29 13:51 ` Richard Stallman
2007-12-29 14:30   ` Thien-Thi Nguyen

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