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From: Steve Kilbane <steve@whitecrow.demon.co.uk>
To: 9fans@cse.psu.edu
Cc: steve@localhost.localdomain
Subject: Re: [9fans] useful language extension, or no?
Date: Tue, 16 Jul 2002 22:29:42 +0100	[thread overview]
Message-ID: <200207162129.WAA00952@localhost.localdomain> (raw)
In-Reply-To: Message from Sam <sah@softcardsystems.com>  of "Tue, 16 Jul 2002 11:05:58 EDT." <Pine.LNX.4.30.0207161101140.14125-100000@athena>


> Suppose I'm not saying "why," but "why not."  IMO it's cleaner

I disagree. It's considerably more ambiguous. Your loop continuation
condition (i<NELS) may be failed by considerably more cases
than your trailing condition (i==NELS). What happens if your loop
body does "i=NELS+1"? What if your "i++" was actually something
like "i=arr[i]"? What if your continuation condition was
"i<NELS && j<NELS2"?

C's "for" is not like Pascal's FOR.

> and
> quite possibly more efficient

The pros and cons have already been discussed. I'd just like to
note that there's no particularly compelling reason why it would
generate different code from that which used the idiom. A good
optimiser would render them into the same internal form anyway.

"A good optimiser" is a subjective term, and Plan 9's C optimising
has already been discussed recent (Summary: it's good enough that
there are more important/interesting/useful things to work on),
but the point stands.

steve




  reply	other threads:[~2002-07-16 21:29 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-07-16 15:53 rob pike, esq.
2002-07-16 15:05 ` Sam
2002-07-16 21:29   ` Steve Kilbane [this message]
     [not found] <sah@softcardsystems.com>
2003-02-15 14:30 ` [9fans] presentation preparation Sam
2003-02-15 19:37   ` Scott Schwartz
2003-02-15 19:48     ` andrey mirtchovski
2003-02-27  9:35       ` Ralph Corderoy
2003-02-28 18:44         ` [9fans] union directories Jack Johnson
2003-02-28 18:53           ` Russ Cox
2003-03-04  9:44           ` Adrian Tritschler
2003-02-15 20:49   ` [9fans] presentation preparation Richard Miller
2003-02-17 15:00   ` Russ Cox
2003-02-17 16:25     ` Fco.J.Ballesteros
  -- strict thread matches above, loose matches on Subject: below --
2002-11-14  6:53 [9fans] how to avoid a memset() optimization Russ Cox
2002-11-14 10:22 ` Douglas A. Gwyn
2002-11-14 13:20   ` Sam
2002-11-14 15:20     ` Scott Schwartz
2002-11-14 15:26       ` Boyd Roberts
2002-11-14 15:34         ` plan9
2002-11-14 15:59           ` Sam
2002-11-14 18:57         ` Steve Kilbane
2002-11-15 10:51           ` Douglas A. Gwyn
2002-11-14 15:50       ` Dan Cross
2002-11-14 17:21         ` Douglas A. Gwyn
2002-11-14 18:51           ` Dan Cross
2002-11-14 15:50     ` Douglas A. Gwyn
2002-11-19  7:20 ` Roman V. Shaposhnick
2002-07-20  5:59 [9fans] useful language extension, or no? forsyth
2002-07-19 18:35 forsyth
2002-07-19 18:33 David Gordon Hogan
2002-07-19 18:22 David Gordon Hogan
2002-07-19 18:36 ` Digby Tarvin
2002-07-19 15:45 forsyth
2002-07-19 18:19 ` Digby Tarvin
2002-07-19  6:48 forsyth
2002-07-19  0:52 David Gordon Hogan
2002-07-19 12:53 ` Digby Tarvin
2002-07-19 15:41   ` Mike Haertel
2002-07-19 18:09     ` Digby Tarvin
2002-07-19 18:38       ` Scott Schwartz
2002-07-19 19:07         ` Digby Tarvin
2002-07-29 16:01     ` Ralph Corderoy
2002-07-18 19:24 David Gordon Hogan
2002-07-19  4:22 ` Lucio De Re
2002-07-18 15:02 forsyth
2002-07-18 23:57 ` arisawa
2002-07-29 15:59   ` Douglas A. Gwyn
2002-07-18 12:54 Richard Miller
2002-07-17 13:36 rob pike, esq.
2002-07-16 17:31 presotto
2002-07-17  8:58 ` William Josephson
2002-07-17  8:58 ` Douglas A. Gwyn
2002-07-16 17:01 forsyth
2002-07-17  8:59 ` Douglas A. Gwyn
2002-07-16 16:50 rob pike, esq.
2002-07-16 15:59 ` Sam
2002-07-16 17:04   ` Howard Trickey
2002-07-16 16:20     ` Sam
2002-07-16 16:08 rob pike, esq.
2002-07-16 15:31 ` Sam
2002-07-16 14:12 Sam
2002-07-16 16:30 ` Boyd Roberts
2002-07-17 12:49 ` Ian Broster
2002-07-17 12:12   ` Sam
2002-07-17 13:33     ` Lucio De Re
2002-07-17 16:12       ` Fariborz (Skip) Tavakkolian
2002-07-17 22:21         ` arisawa
2002-07-17 22:28           ` Ronald G Minnich
2002-07-18  9:51           ` Douglas A. Gwyn
2002-07-18 10:19             ` Lucio De Re
2002-07-18 10:28               ` Lucio De Re
2002-07-18 14:50                 ` Mike Haertel
2002-07-18 14:56                   ` Lucio De Re
2002-07-19  5:23                   ` arisawa
2002-07-18 14:21               ` Douglas A. Gwyn
2002-07-18 14:55                 ` Lucio De Re

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