From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Michael Heerdegen Newsgroups: gmane.emacs.devel Subject: Re: Delimited continuations Date: Sun, 10 Dec 2017 17:53:00 +0100 Message-ID: <87r2s2cyoj.fsf@web.de> References: NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1512924809 13990 195.159.176.226 (10 Dec 2017 16:53:29 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 10 Dec 2017 16:53:29 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sun Dec 10 17:53:24 2017 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eO4qw-0003Kx-G2 for ged-emacs-devel@m.gmane.org; Sun, 10 Dec 2017 17:53:22 +0100 Original-Received: from localhost ([::1]:45186 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eO4r3-0008Nr-HM for ged-emacs-devel@m.gmane.org; Sun, 10 Dec 2017 11:53:29 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:51654) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eO4qx-0008NZ-Jk for emacs-devel@gnu.org; Sun, 10 Dec 2017 11:53:24 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eO4qs-0007zK-Hn for emacs-devel@gnu.org; Sun, 10 Dec 2017 11:53:23 -0500 Original-Received: from mout.web.de ([217.72.192.78]:49486) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1eO4qs-0007yV-2a for emacs-devel@gnu.org; Sun, 10 Dec 2017 11:53:18 -0500 Original-Received: from drachen.dragon ([92.74.165.17]) by smtp.web.de (mrweb102 [213.165.67.124]) with ESMTPSA (Nemesis) id 0McWnE-1efbhb2Do0-00Hce7; Sun, 10 Dec 2017 17:53:15 +0100 In-Reply-To: (John Wiegley's message of "Sat, 09 Dec 2017 01:06:23 -0800") X-Provags-ID: V03:K0:90ndMfSEX2dHopfOwk3QgEhPtRmgq3NyLpQ+FksRyg4Ia30Y2I+ fX+Sl08dJOM+rE/eIUkgR1A9ReBv7MvkEc2sq65ZX5+WXeTsXjRd1cVeb4zXnhnB7Q/x+vQ zT6cY0jkm1MEPQBrVnNSqujLme5d8Y8zIpGVOJy61PStgxidY7T0E5g9FYAKNx1LJWsrUo5 NxSstiPP2R4BqGn9lwL5w== X-UI-Out-Filterresults: notjunk:1;V01:K0:awpybdgI+mM=:NxAxwAxvYAKA0UC/rxNJMK o9VHCRyTut+5m9jGJpq+jrlff+0o0SQe3H+XbC8hMae9/+OhzgpMOa7SMNbNMtHnf8TnX0xJQ +LEMdeL6VqX59IuszU1ty5QHX+E7LS4xrgWzg0h/+wJsHZg4+w6kYRV8+/7Tk2VzO5ss1PXSt NGrwrCPdY3l7QPqHpW++ejQ/mkyl40Bl9Dqv31mB9nro3SYm2FQ+VuNjwQulAOxYmhodOP913 JoJkJxfrNs3FHHJFUW+lnggUa0WsS5+OGtFp4EuH6yiJqt6KYSPYt4M60EB2lIWXJbZVEIVYC Ap5UDOjuDJNEZbq9g/SuKDqgdZa5ibvcEYd30OSSsAN8FVL1wKT7OWiMMf9HNo63Pcm5w/2gA F01PY+owys3bc5O8Xa3vF9sfdDcHEq3DVBjBgb+Kr92nz+Wa7doXoPXazvZkpMgjs/VM22JYl czxV9dJPhEQ3DEIYG8N2KoWhhMCQdGdBntfw6HOPuoQyaKGx69hc3EwzbVPbaQXNVvv9XSfod clTGYIjl9x0wVZ/llWOL2ot5qfcHscyZ84wDfTZQPLaVVyrW5MJbBpJjpw9LWm5utD8X4OPGM hcWE/76RsQRjmuLMQzIWKR9iollcxp1f/V8O/5xHqlWwHgSpljjMAM3lhVi6vIBzIYB00Su8j gUNZSGnkS2Df3MN5O8BOdF9xxQyh49XOPuFBJD0mI711Kh07ge+oK3g6F9IybGE5eheYJeiHl XE/ExUQ9cU7TJ2V6qisGijbLZAl0P9wo1/FJwZ3DMNkc8YDAhYcpBNSHYxsX1HotmDuEE1hi X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 217.72.192.78 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 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" Xref: news.gmane.org gmane.emacs.devel:220850 Archived-At: "John Wiegley" writes: > ;; -*- lexical-binding: t -*- > > (defun shift (k entry) > (if (eq (nth 0 k) 'outer) > (throw (nth 1 k) > (funcall entry #'(lambda (val) > (funcall (nth 2 k) > (list 'inner val))))) > (nth 1 k))) > > (defun reset (thunk) > (let ((bound (make-symbol "reset--bound"))) > (catch bound > (funcall thunk (list 'outer bound thunk))))) This seems to be clever. But one little disadvantage seems to be that a part of the code (the part of the `reset' thunk that is evaluated until `shift' is reached) is processed twice: once till the `shift' is reached (which `throw's and hasn't access to this calculation, so that part of the calculation is thrown away) and a second time when the delimited continuation is called. E.g. in #+begin_src emacs-lisp (reset (lambda (p) (+ (+ 1 2) (shift p (lambda (k) (funcall k 1)))))) #+end_src (+ 1 2) is executed twice. I think this isn't necessarily so? BTW, I wonder what one can potentially do with this stuff. Michael.