From debbugs-submit-bounces@debbugs.gnu.org Tue Nov 03 04:32:25 2020 Received: (at 44254) by debbugs.gnu.org; 3 Nov 2020 09:32:26 +0000 Received: from localhost ([127.0.0.1]:43435 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1kZsfx-0000CI-Jq for submit@debbugs.gnu.org; Tue, 03 Nov 2020 04:32:25 -0500 Received: from eggs.gnu.org ([209.51.188.92]:34664) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1kZsfv-0000Bz-TP for 44254@debbugs.gnu.org; Tue, 03 Nov 2020 04:32:24 -0500 Received: from fencepost.gnu.org ([2001:470:142:3::e]:40433) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kZsfq-0006yJ-BO; Tue, 03 Nov 2020 04:32:18 -0500 Received: from [2a01:e0a:1d:7270:af76:b9b:ca24:c465] (port=58010 helo=ribbon) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1kZsfp-0001aI-GX; Tue, 03 Nov 2020 04:32:17 -0500 From: =?utf-8?Q?Ludovic_Court=C3=A8s?= To: Lars-Dominik Braun Subject: Re: bug#44254: Performance of package input rewriting References: <20201030084245.GB3128@zpidnp36> <87tuuavgg5.fsf@gnu.org> <20201103082343.GC3127@zpidnp36> X-URL: http://www.fdn.fr/~lcourtes/ X-Revolutionary-Date: 13 Brumaire an 229 de la =?utf-8?Q?R=C3=A9volution?= X-PGP-Key-ID: 0x090B11993D9AEBB5 X-PGP-Key: http://www.fdn.fr/~lcourtes/ludovic.asc X-PGP-Fingerprint: 3CE4 6455 8A84 FDC6 9DB4 0CFB 090B 1199 3D9A EBB5 X-OS: x86_64-pc-linux-gnu Date: Tue, 03 Nov 2020 10:32:16 +0100 In-Reply-To: <20201103082343.GC3127@zpidnp36> (Lars-Dominik Braun's message of "Tue, 3 Nov 2020 09:23:43 +0100") Message-ID: <87tuu6g50f.fsf@gnu.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Score: -2.3 (--) X-Debbugs-Envelope-To: 44254 Cc: 44254@debbugs.gnu.org X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: debbugs-submit-bounces@debbugs.gnu.org Sender: "Debbugs-submit" X-Spam-Score: -3.3 (---) Hi, Lars-Dominik Braun skribis: >> I guess it=E2=80=99s easy to end up creating huge object graphs. Here= =E2=80=99s an >> example of an anti-pattern: >>=20 >> (define a >> ((package-input-rewriting x) ((package-input-rewriting y) p1)))=20 >>=20 >> (define b >> ((package-input-rewriting x) ((package-input-rewriting y) p2))) >>=20 >> The correct use is: >>=20 >> (define transform >> (package-input-rewriting (append x y))) >>=20 >> (define a (transform p1)) >> (define b (transform p2)) > that sounds like a section for the cookbook :) Note that there=E2=80=99s a new section in the manual on this topic: https://guix.gnu.org/manual/devel/en/html_node/Defining-Package-Variants.= html >> It seems to me that you=E2=80=99re redefining a dependency graph, node b= y node. >> Thus, you probably don=E2=80=99t need =E2=80=98package-input-rewriting= =E2=80=99 here. What you >> did in Guix-Science commit 972795a23cc9eb5a0bb1a2ffb5681d151fc4d4b0 >> looks more appropriate to me, in terms of style and semantics. > Okay, got it. My initial concern was that rewriting the graph =E2=80=9Cby= hand=E2=80=9D (i.e. > alist-delete) would be tedious and error-prone. I haven=E2=80=99t looked closely enough. If you can define a single proced= ure that rewrites the graph, that=E2=80=99s of course better than rewriting nod= es one by one. Maybe that=E2=80=99s possible, but you need to be careful about factorizing the transformation procedure as I shown above. Thanks, Ludo=E2=80=99.