From: Daniel Colascione <daniel@censorshipresearch.org>
To: Emacs development discussions <emacs-devel@gnu.org>
Subject: Re: O(N^2) behavior in LOOP
Date: Sat, 29 May 2010 18:06:11 -0400 [thread overview]
Message-ID: <4C018FD3.1020305@censorshipresearch.org> (raw)
In-Reply-To: <4C018D79.7040409@censorshipresearch.org>
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On 5/29/10 5:56 PM, Daniel Colascione wrote:
> Before I go fix the loop macro, is there a _reason_ for the nconc silliness?
Err, never mind. LOOP has to work that way. An 'into' variable is
visible; code that LOOP knows nothing about can modify it in arbitrary
ways, which would invalidate any cached tail pointer, ruling out that
approach. Also, code that inspects the variable should see a
representation "as it should be", which rules out a temporarily-reversed
representation, ruling out the push and nconc used in the
anonymous-variable case.
I don't see any way to do better than what LOOP does now without some
kind of code-walker. I still want to fix the anonymous-variable case to
use a tail pointer though.
Sorry for the noise.
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next prev parent reply other threads:[~2010-05-29 22:06 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-29 21:56 O(N^2) behavior in LOOP Daniel Colascione
2010-05-29 22:06 ` Daniel Colascione [this message]
2010-05-29 22:14 ` Lennart Borgman
2010-05-29 22:35 ` Geoff Gole
2010-05-29 23:58 ` [PATCH] use tail pointer for LOOP (Was: Re: O(N^2) behavior in LOOP) Daniel Colascione
2010-05-30 0:45 ` Ken Raeburn
2010-05-30 0:49 ` Daniel Colascione
2010-06-16 17:44 ` tomas
2010-06-16 18:10 ` [PATCH] use tail pointer for LOOP David Kastrup
2010-06-17 5:10 ` tomas
2010-06-17 7:18 ` Thien-Thi Nguyen
2010-06-17 9:22 ` tomas
2010-06-17 10:03 ` Thien-Thi Nguyen
2010-06-17 14:05 ` tomas
2010-06-17 15:16 ` Thien-Thi Nguyen
2010-06-17 10:12 ` Thien-Thi Nguyen
2010-06-17 20:48 ` Stefan Monnier
2010-06-18 7:07 ` David Kastrup
2010-06-18 13:40 ` Stefan Monnier
2010-05-30 17:05 ` Štěpán Němec
2010-05-30 17:09 ` Daniel Colascione
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