From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Sebastian Tennant Newsgroups: gmane.lisp.guile.user Subject: Re: Dynamic variable binding Date: Fri, 19 Dec 2008 11:50:11 +0000 Message-ID: References: <8wro202o.fsf@vps203.linuxvps.org> <200811130051.mAD0pReg006490@fcs13.keithdiane.us> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: ger.gmane.org 1229687415 25494 80.91.229.12 (19 Dec 2008 11:50:15 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 19 Dec 2008 11:50:15 +0000 (UTC) To: guile-user@gnu.org Original-X-From: guile-user-bounces+guile-user=m.gmane.org@gnu.org Fri Dec 19 12:51:21 2008 Return-path: Envelope-to: guile-user@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.50) id 1LDdt2-0008Jy-1c for guile-user@m.gmane.org; Fri, 19 Dec 2008 12:51:20 +0100 Original-Received: from localhost ([127.0.0.1]:41042 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LDdrp-0002dq-Qc for guile-user@m.gmane.org; Fri, 19 Dec 2008 06:50:05 -0500 Original-Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LDdrm-0002ck-5m for guile-user@gnu.org; Fri, 19 Dec 2008 06:50:02 -0500 Original-Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LDdrl-0002cJ-RE for guile-user@gnu.org; Fri, 19 Dec 2008 06:50:01 -0500 Original-Received: from [199.232.76.173] (port=35505 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LDdrl-0002cE-Iz for guile-user@gnu.org; Fri, 19 Dec 2008 06:50:01 -0500 Original-Received: from main.gmane.org ([80.91.229.2]:35057 helo=ciao.gmane.org) by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LDdrk-0006PH-Vx for guile-user@gnu.org; Fri, 19 Dec 2008 06:50:01 -0500 Original-Received: from list by ciao.gmane.org with local (Exim 4.43) id 1LDdrf-00037s-RI for guile-user@gnu.org; Fri, 19 Dec 2008 11:49:55 +0000 Original-Received: from vps203.linuxvps.org ([91.186.7.203]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 19 Dec 2008 11:49:55 +0000 Original-Received: from sebyte by vps203.linuxvps.org with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 19 Dec 2008 11:49:55 +0000 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 66 Original-X-Complaints-To: usenet@ger.gmane.org X-Gmane-NNTP-Posting-Host: vps203.linuxvps.org User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/22.2 (gnu/linux) Cancel-Lock: sha1:2QLJtBWoBeufreSdshX5P3eBVoE= X-detected-operating-system: by monty-python.gnu.org: GNU/Linux 2.6, seldom 2.4 (older, 4) X-BeenThere: guile-user@gnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: General Guile related discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: guile-user-bounces+guile-user=m.gmane.org@gnu.org Errors-To: guile-user-bounces+guile-user=m.gmane.org@gnu.org Xref: news.gmane.org gmane.lisp.guile.user:7023 Archived-At: > Quoth Keith Wright : >> From: Sebastian Tennant >> >> guile> (define-macro (definer var val) >> `(define ,var ,val)) >> guile> (definer 'foo "bar") >> guile> foo >> ERROR: Unbound variable: foo >> ABORT: (unbound-variable) >> >> No doubt this fails for the same reason this does: >> >> guile> (define 'foo "bar") >> guile> foo >> ERROR: Unbound variable: foo >> ABORT: (unbound-variable) >> >> What exactly happens when you 'define' a symbol? > I don't know what happens (in Guile), but I can tell > you what _should_ happen. (In my humble opinion as > a demi-god of semantics.) I'm trying to wrap my head around symbols, variables and names of variables. They seem to me to be three different things. > (define 'foo "bar") > > There are several possibilities > > (1) error message in define > (1a) Rude: Thou fool! |quote| is not a variable > (1b) Polite: If you are sure you want to do that, > write out the quote, don't use apostrophe > (1c) Obscure: Bad variable in def_schkdt To be really semantically accurate should we not say: (1a) Thou irrepressible fool! |quote| cannot be the _name_ of a variable. (1c) Obscure: Bad variable _name_ in def_schkdt. > But you are asking the wrong question. Ask not > what happens when a symbol is defined, ask what > you can do to make the macro define an unquoted > variable. Answer: Pass it an unquoted variable. (define-macro (definer var val) `(define ,var ,val)) => (definer foo "bar") => foo => "bar" :) Is that the answer you expected? My semantic point is that the first argument to definer (above) is not a symbol and it's not a variable (an unbound variable error would be thrown if it was), so in the context of the first agument to define there is a third data type; 'variable name'. Sebastian