From: Gdobbins <gdobbins@protonmail.com>
To: rms@gnu.org
Cc: John Wiegley <jwiegley@gmail.com>,
schwab@linux-m68k.org, lokedhs@gmail.com, emacs-devel@gnu.org
Subject: Re: [PATCH] Add new lisp function length= with bytecode support
Date: Mon, 06 Mar 2017 15:36:59 -0500 [thread overview]
Message-ID: <drR9cuRr2GSFjjmJC-diuRAWnYJxzfjnCbf_-JzPWypIvKRm2UMZ6TvUdc9qBSZN-iqP3YVBTip57OETjkGXH8GQ2Yj-a3WclGdslq9KKDI=@protonmail.com> (raw)
In-Reply-To: <E1ckwvw-0001dN-Mt@fencepost.gnu.org>
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> Why add length= as a primitive? Why is it important enough to justify that?
About 14% of all calls to length are then simply compared via =. I checked and the < and > variants combined account for about 30%, the <= and >= combined about 10%. I don't really see a purpose in using nthcdr like you have in a lisp implementation of length=, it isn't any better than just using length directly since it requires just as much linked list traversal. That was of course the reason I implemented it in C.
> Wouldn't it make sense to have a function ‘length<’ and ‘length>’ as well?
Yes, it would appear so. But for the same reasons as length= they would need to be implemented in C for there to be any improvement in efficiency. They could be added to the < and > bytecodes in the same way that I've done with = and length=.
-- Graham Dobbins
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next prev parent reply other threads:[~2017-03-06 20:36 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-26 22:04 [PATCH] Add new lisp function length= with bytecode support Gdobbins
2017-02-27 16:14 ` Eli Zaretskii
2017-02-27 18:43 ` Gdobbins
2017-02-27 23:06 ` Paul Eggert
2017-02-28 0:35 ` Gdobbins
2017-02-28 9:24 ` Andreas Schwab
2017-03-06 1:59 ` Gdobbins
2017-03-06 6:13 ` Elias Mårtenson
2017-03-06 7:43 ` John Wiegley
2017-03-06 18:00 ` Richard Stallman
2017-03-06 20:36 ` Gdobbins [this message]
2017-03-06 20:45 ` Clément Pit-Claudel
2017-03-06 21:03 ` Gdobbins
2017-03-07 0:29 ` Gdobbins
2017-03-10 10:20 ` Ken Raeburn
2017-03-10 22:25 ` Gdobbins
2017-03-13 2:51 ` Gdobbins
2017-03-13 3:20 ` Stefan Monnier
2017-03-14 6:06 ` Gdobbins
-- strict thread matches above, loose matches on Subject: below --
2017-03-07 13:52 Constantin Kulikov
2017-03-08 2:00 ` Gdobbins
2017-03-08 2:46 ` Stefan Monnier
2017-03-08 3:31 ` Gdobbins
2017-03-08 4:13 ` Stefan Monnier
2017-03-08 7:01 ` Gdobbins
2017-03-08 16:47 ` Stefan Monnier
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