From cowan@ccil.org Wed Oct 22 20:51:37 2008 Received: with ECARTIS (v1.0.0; list llg-board); Wed, 22 Oct 2008 20:51:37 -0700 (PDT) Received: from earth.ccil.org ([192.190.237.11]) by chain.digitalkingdom.org with esmtp (Exim 4.69) (envelope-from ) id 1KsrEU-0000jx-Na for llg-board@lojban.org; Wed, 22 Oct 2008 20:51:37 -0700 Received: from cowan by earth.ccil.org with local (Exim 4.63) (envelope-from ) id 1KsrET-0000OH-Jb for llg-board@lojban.org; Wed, 22 Oct 2008 23:51:33 -0400 Date: Wed, 22 Oct 2008 23:51:33 -0400 To: llg-board@lojban.org Subject: [llg-board] Re: A request to spend money. Message-ID: <20081023035133.GE4608@mercury.ccil.org> References: <20081022214253.GD23512@digitalkingdom.org> <20081022223521.GB31254@mercury.ccil.org> <20081022225329.GG23512@digitalkingdom.org> <20081022232701.GH23512@digitalkingdom.org> <20081023011215.GI23512@digitalkingdom.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.13 (2006-08-11) From: John Cowan X-Spam-Score: -0.2 X-Spam-Score-Int: -1 X-Spam-Bar: / X-archive-position: 431 X-ecartis-version: Ecartis v1.0.0 Sender: llg-board-bounce@lojban.org Errors-to: llg-board-bounce@lojban.org X-original-sender: cowan@ccil.org Precedence: bulk Reply-to: llg-board@lojban.org X-list: llg-board Matt Arnold scripsit: > I don't understand that either. I thought code, by virtue of being > code, has to be rigorously formalized in order for a computer to be > able to understand the instructions. That can't be what you mean, so > I'm confused. That's true in one sense. But there are two kinds of formal description: a program is a formal description of what the computer is to do, blow by blow, like a recipe or knitting instructions. A formal grammar, on the other hand, is a formal description of what the input to a program looks like, without any specification of how the program is to verify its input against that grammar. Given a grammar, it's possible to construct a program that detects that grammar and complains when the input violates it. However, not every formal grammar is usable in constructing such a program; it may need help from auxiliary programs. A PEG grammar is something in between: it specifies the valid inputs, but also an order in which its rules are to be tried. The YACC and BNF grammars have no such notion. I hope that helps. -- John Cowan http://ccil.org/~cowan cowan@ccil.org Arise, you prisoners of Windows / Arise, you slaves of Redmond, Wash, The day and hour soon are coming / When all the IT folks say "Gosh!" It isn't from a clever lawsuit / That Windowsland will finally fall, But thousands writing open source code / Like mice who nibble through a wall. --The Linux-nationale by Greg Baker