From owner-cvs-all  Thu Jan  3  3:42:20 2002
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Date: Thu, 3 Jan 2002 12:42:02 +0100 (CET)
From: Harti Brandt <brandt@fokus.gmd.de>
To: Poul-Henning Kamp <phk@critter.freebsd.dk>
Cc: Julian Elischer <julian@elischer.org>,
	Stephen McKay <mckay@thehub.com.au>, John Baldwin <jhb@FreeBSD.ORG>,
	<cvs-all@FreeBSD.ORG>, <cvs-committers@FreeBSD.ORG>,
	Julian Elischer <julian@FreeBSD.ORG>, Greg Lehey <grog@FreeBSD.ORG>
Subject: Re: cvs commit: src/share/man/man3 queue.3 
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On Thu, 3 Jan 2002, Poul-Henning Kamp wrote:

PK>In message <Pine.BSF.4.21.0201030044520.22265-100000@InterJet.elischer.org>, Ju
PK>lian Elischer writes:
PK>
PK>>> >how about explicitly detailing that it's NULL at the end?
PK>>> >Doesn't that also work?
PK>>>
PK>>> I don't think we should document that.
PK>>>
PK>>> There are types of lists/queues which doesn't naturally end with
PK>>> that condition.  That is why we have the FOO_EMPTY() clause, although
PK>>> people tend to also rely on
PK>>>
PK>>> 	if (FOO_FIRST(...) == NULL)
PK>>> 		/* nothing to do */
PK>>
PK>>Since TAILQ_FIRST== NULL is a termination (it's empty)
PK>>condition (as is TAILQ_NEXT() == NULL)
PK>>it makes PERFECT sense that a completed set of iterations ends up
PK>>with the pointer being NULL.
PK>
PK>If for instance we (re)introduce CIRCLEQ or certain other queue
PK>types, it is by no means obvious that the continuation clause
PK>of the FOREACH() will be "!= NULL".

That means, that the "== NULL" should be documented exactly for those
queue types for which this is true.

harti
-- 
harti brandt, http://www.fokus.gmd.de/research/cc/cats/employees/hartmut.brandt/private
              brandt@fokus.fhg.de


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