From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Po Lu Newsgroups: gmane.emacs.devel Subject: Hash consing (was: Re: sqlite3) Date: Sat, 18 Dec 2021 17:35:56 +0800 Message-ID: <87ee6afe6b.fsf_-_@yahoo.com> References: <87tufmjyai.fsf@gnus.org> <87lf0nr2b4.fsf@gnus.org> <87fsqvp5ae.fsf@gnus.org> <87bl1jp51y.fsf@gnus.org> <187323C2-81D0-47B6-96C8-3D721EF7C003@mit.edu> <8735mvp454.fsf@gnus.org> <87ilvn1xur.fsf@gnus.org> <87fsqqxsr9.fsf@gnus.org> <679ECACB-C458-4C9E-B26A-72E8D81E0A24@mit.edu> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="20822"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.60 (gnu/linux) Cc: "emacs-devel@gnu.org" To: LdBeth Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sat Dec 18 10:36:56 2021 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1myW9A-0005Bg-7i for ged-emacs-devel@m.gmane-mx.org; Sat, 18 Dec 2021 10:36:56 +0100 Original-Received: from localhost ([::1]:39308 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1myW99-0007TF-0V for ged-emacs-devel@m.gmane-mx.org; Sat, 18 Dec 2021 04:36:55 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:47522) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1myW8R-00061g-Q1 for emacs-devel@gnu.org; Sat, 18 Dec 2021 04:36:11 -0500 Original-Received: from sonic316-22.consmr.mail.ne1.yahoo.com ([66.163.187.148]:40188) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1myW8O-0005GV-IJ for emacs-devel@gnu.org; Sat, 18 Dec 2021 04:36:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s2048; t=1639820165; bh=EwjS2ksra4yRgwVx49gWN8Rut8QF8+iBPHwSsHEujVk=; h=From:To:Cc:Subject:References:Date:In-Reply-To:From:Subject:Reply-To; b=NbgNB2dfu4OW6uK5CkgTRdISuj1E9+2NXuJdRxTBCD+4EG9oKa7/KI+Mbf+k8tMBgpAxtI4RP5O4/yNBdx6VWPdZOLzt2n8g0eiAmL+pKJynxaoB1IQfOekjMxtHDni5HMK/JF0gqsTpEfGQ64i8RXpWJPbogq2dslx9IJOohl5FmS43cB4ZSyguRRpMOx3pEvKk+wN7NMMVVqvQyaWZVKWohMl2ZGw883fVRTh2o0CtjYVETcP/XBq2plcJEuW0moFNpIKoSnMdj8jBP6Fyi5p3+hw5bHajFKvy5cgQWjkte9LttW9twXWf7Ukz1EgfPk/JZZRdQCn3PCTJvhDqWQ== X-SONIC-DKIM-SIGN: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s2048; t=1639820165; bh=tBCeURdXiyht6+fUG6D02h8tobyGHrFifuIgQw+Mx5Y=; h=X-Sonic-MF:From:To:Subject:Date:From:Subject; b=M5d4mJT/F029gtRsxJabEqTwYcGxSay2erEJeFtWZX0x2bmnIrzfw0fUdsG/EGJ5WmoewNZxkakZuJ5ICl7N+uCWcx5B5yf2rnpzSQFuBsGVx1W1LaeQwAFrRHzdYx2QfTXZaVWAAo2yQ8209SsTc7UgeyLjyP0UplWwidowzraOwQpsNVATSyRgLsMeir9Zz7ruempsgRXlXwtkGfB3OYBGgY1J9C66Rcrq/S56Tm5p13nNpJ8PcBcEzwbrvuOeJJZ2AKQibgyt3fc+NXwrZF3kCvp5mvchV04s6io8zyanfMeN2NJl1mJHQFMjE7v+NDlxTriyP7NsoBFGAX0nDw== X-YMail-OSG: yODEmu8VM1nMmRJ9tCeTYujodXqAgVc8oidU1Adi9z71NyFE5qvXmjmg_N38OAe pP9h14UNQsKMxzcoTFTl34MRYmPBaMLYv4Iu7Co1kpIvA0iwe.c2_KXYxg4wIwcHU3sJsKWDCPAH WkC_Wrj7XAOyUmqBHT9ZbMfldaSJtusAFKaJuz4QXDGiECA1cixOVyvNNW0STdL0omzVBIBbZ7Mt a8q95LnkW8S6e3WXsuVEEONKXTsKjNQQtH2kSBsaP3G9vpzhgB47AJXL6kEjySBBssSx_W37_MHD OiHxJLtWgh1ZdhZC3rZJwkwlSNA1F_e8xUI9hkyjQuKL3V4l1U6DLEmp3MneZo212U6mYsMJjfpl uV20M33H3CeG1Orox5fQotdlWi888gf_RohCf46R.2s2U0ntT0l3Rrmv0Y5MCCmCYHI8uelI5b3W t2ccPSIu0waWPPK7vHMnZTgwVUphXvMgr2PdgBYCcrPfas7ZzziVIHT2FihLBL0DNhrjBfwpf.n. m5680AEBFnnPTPblRp9EHHOEQKOSdZ7wT.PflMn5Fn7P7aDHgd6WrbWnlv5XFb1IFi9b67wQ84KM ZD8CI0Gob_3WDzQMjVanzxt7NYOyhoDQuH89jCiykOkXc9hvJtKFaydnbYOzP9S0En0jxsSLOgTz ytbL0zMgnrt5mLMSLqeLdm30b5Z9Smx6qcBuDrAJ5JG1uZn2VHnXSdykN2U3FsAKweOZNCyDjKkc cqkU0.Ht0MPD4HI19VnhTOI.ZncyrLHsaea5vUbz8hJTf.yeIuv.aOrHIMHC1Izm5ENC_yGIGP8P PDngilDEZnqdx3x7A1d5AdXgNh9IE1r3QpXyWoCfN. X-Sonic-MF: Original-Received: from sonic.gate.mail.ne1.yahoo.com by sonic316.consmr.mail.ne1.yahoo.com with HTTP; Sat, 18 Dec 2021 09:36:05 +0000 Original-Received: by kubenode515.mail-prod1.omega.sg3.yahoo.com (VZM Hermes SMTP Server) with ESMTPA ID 7d736bb7c9959911035d769842910bd9; Sat, 18 Dec 2021 09:36:00 +0000 (UTC) In-Reply-To: (LdBeth's message of "Sat, 18 Dec 2021 16:52:03 +0800") X-Mailer: WebService/1.1.19498 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.yahoo Received-SPF: pass client-ip=66.163.187.148; envelope-from=luangruo@yahoo.com; helo=sonic316-22.consmr.mail.ne1.yahoo.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:282272 Archived-At: LdBeth writes: > It seems no one has yet pointed out "preserving EQness" is actually > hash-consing[1], a technique has been developed in Lisp and now well > known in Functional Programming communities. > > It has main features that: > > 1. Keeps only one copy of (structurally) EQUAL objects and therefore > 2. reduce storage usage > 3. reduce the time needed to do a EQUAL comparsion to EQ. > 4. useful for function memoization > > It is definitely useful, but I think we could make it into a separated > package, probably. I wonder how hash consing would make sense in a language like Emacs Lisp that has `rplaca' and `rplacd'. Perhaps we would need some kind of immutable cons data type.