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Date: Thu, 3 Jan 2002 01:43:02 -0800 (PST)
From: Julian Elischer <julian@elischer.org>
To: Matthew Dillon <dillon@apollo.backplane.com>
Cc: Poul-Henning Kamp <phk@critter.freebsd.dk>,
	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, Matthew Dillon wrote:

> 
> 
>     The issue here is to extend an abstraction up to the point where
>     the compiler can easily optimize it.

Bugger the compiler, I want readable code..
:-)

> 
>     Most of the lists I use are implemented circularly internally,
>     allowing addhead, addtail, insertbefore, insertafter, and remove
>     functions to be implemented with no conditionals.  In this case
>     the terminator is a pointer back to the list head.
> 
>     Now consider a MYLIST_EMPTY() macro verses a MYLIST_GETHEAD()
>     macro.  MYLIST_GETHEAD() would have to check for the terminating
>     condition (a conditional) and return NULL if it's true and the head
>     node if it is false.  MYLIST_EMPTY() simply checks the terminating
>     condition and returns a boolean.  Now consider this code:

I don't understand your point..
TAILQ_FIRST() does not do a conditional to give a NULL on empty..
...#define TAILQ_FIRST(head)       ((head)->tqh_first)





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