From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Michael Heerdegen Newsgroups: gmane.emacs.devel Subject: Re: Generators (iterators) for Gnu Emacs Date: Fri, 05 Dec 2014 19:01:27 +0100 Message-ID: <871toern60.fsf@web.de> References: <877fy77zhp.fsf@web.de> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1417802536 28087 80.91.229.3 (5 Dec 2014 18:02:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 5 Dec 2014 18:02:16 +0000 (UTC) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Fri Dec 05 19:02:09 2014 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1XwxCa-0004WR-Is for ged-emacs-devel@m.gmane.org; Fri, 05 Dec 2014 19:02:00 +0100 Original-Received: from localhost ([::1]:51767 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XwxCa-0006e9-8Y for ged-emacs-devel@m.gmane.org; Fri, 05 Dec 2014 13:02:00 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:47293) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XwxCR-0006X9-7g for emacs-devel@gnu.org; Fri, 05 Dec 2014 13:01:57 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XwxCL-0003iC-6C for emacs-devel@gnu.org; Fri, 05 Dec 2014 13:01:51 -0500 Original-Received: from plane.gmane.org ([80.91.229.3]:53205) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XwxCK-0003i1-WD for emacs-devel@gnu.org; Fri, 05 Dec 2014 13:01:45 -0500 Original-Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1XwxCJ-0004KC-CW for emacs-devel@gnu.org; Fri, 05 Dec 2014 19:01:43 +0100 Original-Received: from ip-90-186-215-205.web.vodafone.de ([90.186.215.205]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 05 Dec 2014 19:01:43 +0100 Original-Received: from michael_heerdegen by ip-90-186-215-205.web.vodafone.de with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 05 Dec 2014 19:01:43 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 46 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: ip-90-186-215-205.web.vodafone.de User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) Cancel-Lock: sha1:ZCuUbHzwcfsSbB/s5qXUVTCwrus= X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 80.91.229.3 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 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.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:178968 Archived-At: Stefan Monnier writes: > A few comments below. Thanks. Still using the term "generator" to avoid confusion, though I'm going to rename the thing to "iterator". > It's great to see that you haven't needed anything else than `gen-next'. > I'd have expected a `gen-done-p' test to be needed/handy every once in > a while. Dunno if that would be useful, I never missed it, but it should be trivial to introduce. > I guess a `gen-cons' would be more efficient than this > (gen-append (gen-from-elts value) ...). I'm not sure implementing `gen-cons' is a good idea. Generators are not built from conses - but having `gen-cons' would allow to build generator pseudo lists. This package is about introducing a different concept. Plus, using `gen-cons' as a building block of generators would create deeply nested lambdas that would soon hit `max-lisp-eval-depth' when requesting elements. Avoiding recursion, which Emacs is not good at, is crucial allover in this package. Pushing to generators should not be needed repeatedly - if you think you want this, use lists. In the above case, it is just coincidence that the first generator has only one element. And I don't think efficiency is an issue here. If you think it is I will rewrite that code, but avoiding a `gen-cons'. > > (defmacro gen-delay-expr (expression) > > Have you made use of this? I'm not sure it really fits. I mean, > technically it works, but I'm not completely sure if pretending it's > a generator is a clever idea or not. I defined it because I need it in `gen-cache', and because it wasn't existing yet in Emacs. Do you think delay-expression should be defined somewhere else in Emacs? Then I would be happy to use it for `gen-cache'. Thanks, Michael.