From: Tom Tromey <tromey@redhat.com>
To: Dmitry Antipov <dmantipov@yandex.ru>
Cc: Emacs development discussions <emacs-devel@gnu.org>
Subject: Re: [RFC] caar/cadr/cdar/cddr
Date: Thu, 12 Jul 2012 10:47:42 -0600 [thread overview]
Message-ID: <87ehohc4ep.fsf@fleche.redhat.com> (raw)
In-Reply-To: <4FFEFA98.3060509@yandex.ru> (Dmitry Antipov's message of "Thu, 12 Jul 2012 20:26:00 +0400")
>>>>> "Dmitry" == Dmitry Antipov <dmantipov@yandex.ru> writes:
Dmitry> These are widely used, so why not doing them as C primitives and
Dmitry> corresponding bytecodes? It shouldn't be too hard to tweak
Dmitry> byte-opt.el to optimize (car (cdr X)) -> (cadr X) etc., and so
Dmitry> emit new bytecodes.
Did you try to measure the performance benefit?
Dmitry> +(byte-defop 48 0 byte-caar)
Dmitry> +(byte-defop 49 0 byte-cadr)
Dmitry> +(byte-defop 50 0 byte-cdar)
Dmitry> +(byte-defop 51 0 byte-cddr)
Occasionally I wish we were sharing these definitions with bytecode.c;
or more generally that parts of the Emacs core could be written in some
form of Lisp.
Dmitry> + loop:
Dmitry> + if (CONSP (tem))
Dmitry> + {
Dmitry> + if (!EQ (tem, list))
Dmitry> + return XCAR (tem);
Dmitry> + tem = XCDR (tem);
Dmitry> + goto loop;
Dmitry> + }
Dmitry> + else return NILP (tem) ? Qnil : wrong_type_argument (Qlistp, tem);
All these functions are implemented in what seems, to me, a very weird
way. Why not just write the obvious straight-line code?
Tom
next prev parent reply other threads:[~2012-07-12 16:47 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-12 16:26 [RFC] caar/cadr/cdar/cddr Dmitry Antipov
2012-07-12 16:47 ` Tom Tromey [this message]
2012-07-12 16:53 ` Tom Tromey
2012-07-12 16:53 ` Paul Eggert
2012-07-12 17:44 ` Dmitry Antipov
2012-07-12 21:46 ` Samuel Bronson
2012-07-12 22:43 ` Paul Eggert
2012-07-12 23:08 ` Alp Aker
2012-07-13 0:12 ` Stefan Monnier
2012-07-13 1:27 ` Samuel Bronson
2012-07-13 12:05 ` Stefan Monnier
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