Received: from sog-mx-4.v43.ch3.sourceforge.com ([172.29.43.194] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1Rgb9t-0003ZE-MO for bitcoin-development@lists.sourceforge.net; Fri, 30 Dec 2011 12:02:01 +0000 Received-SPF: pass (sog-mx-4.v43.ch3.sourceforge.com: domain of gmail.com designates 209.85.212.175 as permitted sender) client-ip=209.85.212.175; envelope-from=chris.double@gmail.com; helo=mail-wi0-f175.google.com; Received: from mail-wi0-f175.google.com ([209.85.212.175]) by sog-mx-4.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1Rgb9r-0002lC-EY for bitcoin-development@lists.sourceforge.net; Fri, 30 Dec 2011 12:02:01 +0000 Received: by wibhq7 with SMTP id hq7so10398852wib.34 for ; Fri, 30 Dec 2011 04:01:53 -0800 (PST) MIME-Version: 1.0 Received: by 10.180.19.138 with SMTP id f10mr108153230wie.3.1325246513327; Fri, 30 Dec 2011 04:01:53 -0800 (PST) Sender: chris.double@gmail.com Received: by 10.223.104.206 with HTTP; Fri, 30 Dec 2011 04:01:53 -0800 (PST) In-Reply-To: References: <1325148259.14431.140661016987461@webmail.messagingengine.com> Date: Sat, 31 Dec 2011 01:01:53 +1300 X-Google-Sender-Auth: hD_ca5PSJUaOh1upT7w5Ki5wBKU Message-ID: From: Chris Double To: bitcoin-development@lists.sourceforge.net Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Spam-Score: -1.5 (-) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (chris.double[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-Headers-End: 1Rgb9r-0002lC-EY Subject: Re: [Bitcoin-development] Alternative to OP_EVAL X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 30 Dec 2011 12:02:01 -0000 On Fri, Dec 30, 2011 at 5:42 AM, wrote: > Basically OP_DUP lets you duplicate the code on the stack and that is the > key to looping. =A0I'm pretty sure from here we get get Turing completene= ss. > Using the stack operations I expect you can implement the SK-calculus > given an OP_EVAL that allows arbitrary depth. > > OP_EVAL adds dangerously expressive power to the scripting language. If you look at the archives of the concatenative programming mailing list [1] you'll see lots of examples of people creating stack languages with minimal operations that exploit similar functionality to reduce the required built in operations. The discussion on the list is mostly about stack based languages where programs can be pushed on the stack and executed (eg. Joy [2]/Factor/Some Forths). I don't think the scripting engine in bitcoin has the ability to concatenate, append or otherwise manipulate scripts on the stack to be eval'd though does it? [1] http://tech.groups.yahoo.com/group/concatenative [2] http://tunes.org/~iepos/joy.html Chris. --=20 http://www.bluishcoder.co.nz