From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.windriver.com ([147.11.1.11]) by linuxtogo.org with esmtp (Exim 4.72) (envelope-from ) id 1SUN9U-0003eu-5L for openembedded-core@lists.openembedded.org; Tue, 15 May 2012 21:11:20 +0200 Received: from ALA-HCA.corp.ad.wrs.com (ala-hca [147.11.189.40]) by mail.windriver.com (8.14.3/8.14.3) with ESMTP id q4FJ1JfR027542 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=FAIL) for ; Tue, 15 May 2012 12:01:19 -0700 (PDT) Received: from wrlaptop (172.25.40.226) by ALA-HCA.corp.ad.wrs.com (147.11.189.50) with Microsoft SMTP Server id 14.1.255.0; Tue, 15 May 2012 12:01:18 -0700 Date: Tue, 15 May 2012 14:01:10 -0500 From: Peter Seebach To: "openembedded-core@" Message-ID: <20120515140110.2ba5a1be@wrlaptop> X-Mailer: Claws Mail 3.7.8 (GTK+ 2.24.4; x86_64-pc-linux-gnu) MIME-Version: 1.0 Subject: RFC: FOO_subtract, the logical antidote to FOO_append. X-BeenThere: openembedded-core@lists.openembedded.org X-Mailman-Version: 2.1.11 Precedence: list Reply-To: Patches and discussions about the oe-core layer List-Id: Patches and discussions about the oe-core layer List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 15 May 2012 19:11:20 -0000 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit There's a few cases where something is a huge list of space-separated things, and it is desireable to remove one. The example currently afflicting me is DISTRO_FEATURES_LIBC_DEFAULT; I want to end up with the distro features including all but one of the words in it. It seems to me that a counterpart to _append would make sense. Here is my basic idea: FOO_subtract = "..." means that, when you expand FOO: 1. Fully expand it. 2. Fully expand FOO_subtract. 3. Remove any words in FOO_subtract from FOO. 4. Yield the result. The rationale is that the semantics of things where we're using _append seem to be consistently of the form "this is a space-separated set", and being able to remove things from a set would be Super Handy. So I'm proposing the semantics for consideration, and if people like them, I will go try to implement it in my Copious Free Time. -s -- Listen, get this. Nobody with a good compiler needs to be justified.