From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Alan Mackenzie <acm@muc.de>
Cc: martin rudalics <rudalics@gmx.at>, emacs-devel@gnu.org
Subject: Re: Problems with syntax-ppss
Date: Sat, 05 Apr 2008 14:37:39 -0400 [thread overview]
Message-ID: <jwv63uwxijb.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <20080405144642.GA3095@muc.de> (Alan Mackenzie's message of "Sat, 5 Apr 2008 14:46:42 +0000")
>> >I strongly recommend to always call syntax-ppss in a widened buffer.
>> ... and with match-data saved.
> Er, your replies don't exactly radiate an aura of confidence about
> syntax-ppss. ;-(
> I think you (Stefan) 're saying that the function isn't 100% defined for
> a narrowed buffer.
Indeed.
> Will calling s-ppss on a narrowed buffer corrupt the
> cache at all, for example?
Yes it can. Similarly the cache does not keep track of the syntax-table
so if you switch syntax-table between calls you may get unexpected results.
> As a matter of interest, are there any benchmark figures for s-ppss?
I did time it in various circumstances when writing it (so as to tune
its algorithm).
> Like, how many characters do you have to scan more than, before s-ppss
> (an interpreted lisp function) starts being faster than
> (parse-partial-sexp 1 (point)) (a fast function written in C)?
I can't remember exactly, but syntax-ppss-max-span was set based on
these measurements, so it gives you an idea. Note that there are two
different caches: there's syntax-ppss-cache which is affected by
syntax-ppss-max-span and is only really useful for large buffers, and
there's syntax-ppss-last which benefit from spatial locality.
Stefan
next prev parent reply other threads:[~2008-04-05 18:37 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-04 17:26 Problems with syntax-ppss Alan Mackenzie
2008-04-04 17:29 ` Lennart Borgman (gmail)
2008-04-04 20:24 ` Stefan Monnier
2008-04-04 21:14 ` martin rudalics
2008-04-05 14:46 ` Alan Mackenzie
2008-04-05 18:37 ` Stefan Monnier [this message]
2008-04-06 14:07 ` Alan Mackenzie
2008-04-07 14:57 ` Stefan Monnier
2008-04-07 15:14 ` Lennart Borgman (gmail)
2008-04-07 16:43 ` Stefan Monnier
2008-04-07 14:59 ` Stefan Monnier
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