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From: David Kastrup <dak@gnu.org>
To: rms@gnu.org
Cc: Alan Mackenzie <acm@muc.de>, emacs-devel@gnu.org
Subject: Re: How about text-property-functions using `equal' rather than `eq'?
Date: Tue, 05 Feb 2008 09:48:38 +0100	[thread overview]
Message-ID: <86ve53okk9.fsf@lola.quinscape.zz> (raw)
In-Reply-To: <E1JMIn0-0007ZQ-NH@fencepost.gnu.org> (Richard Stallman's message of "Tue, 05 Feb 2008 03:04:22 -0500")

Richard Stallman <rms@gnu.org> writes:

>     All the built in text property functions which compare properties appear
>     to use `eq' for the comparison.  Some of these actually say this in
>     their doc-strings or the pertinent manual page, some of them might
>     actually say it in both.  ;-(
>
> `eq' is faster,

More importantly, it is constant time.

>     I would dearly love to use text-property-any to locate such a
>     buffer position, but unfortunately (eq '(1) '(1)) => nil.  :-( So
>     I've had to code up a clumsy equivalent which will certainly be
>     much slower.
>
> You can write code which uses the primitives to find the next non-eq
> property, then comparing it with equal and looping so that you find
> the next non-equal property.

One can also see where the constant '(1) is created and keep a copy of
that for eq-comparison.

-- 
David Kastrup




      reply	other threads:[~2008-02-05  8:48 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-04 20:53 How about text-property-functions using `equal' rather than `eq'? Alan Mackenzie
2008-02-05  8:04 ` Richard Stallman
2008-02-05  8:48   ` David Kastrup [this message]

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