From: roconnor@theorem•ca
To: bitcoin-development@lists•sourceforge.net
Subject: Re: [Bitcoin-development] Alternative to OP_EVAL
Date: Thu, 29 Dec 2011 11:42:56 -0500 (EST) [thread overview]
Message-ID: <alpine.LRH.2.00.1112291135040.22327@theorem.ca> (raw)
In-Reply-To: <1325148259.14431.140661016987461@webmail.messagingengine.com>
On Thu, 29 Dec 2011, theymos wrote:
> On Thu, Dec 29, 2011, at 01:55 AM, roconnor@theorem•ca wrote:
>> The number of operations executed is still bounded by the number of
>> operations occurring in the script. With the OP_EVAL proposal the
>> script language becomes essentially Turing complete, with only an
>> artificial limit on recursion depth preventing arbitrary computation
>> and there is no way to know what code will run without executing it.
>
> Even if OP_EVAL allowed infinite depth, you'd still need to explicitly
> specify all operations performed, since there is no way of looping.
That's not true. Gavin himself showed how to use OP_EVAL to loop:
OP_PUSHDATA {OP_DUP OP_EVAL} OP_DUP OP_EVAL.
Basically OP_DUP lets you duplicate the code on the stack and that is the
key to looping. I'm pretty sure from here we get get Turing completeness.
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.
--
Russell O'Connor <http://r6.ca/>
``All talk about `theft,''' the general counsel of the American Graphophone
Company wrote, ``is the merest claptrap, for there exists no property in
ideas musical, literary or artistic, except as defined by statute.''
next prev parent reply other threads:[~2011-12-29 16:43 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-29 6:55 roconnor
2011-12-29 8:44 ` theymos
2011-12-29 16:42 ` roconnor [this message]
2011-12-30 12:01 ` Chris Double
2011-12-30 17:19 ` roconnor
2012-01-02 15:14 ` Stefan Thomas
2012-01-02 15:59 ` Gavin Andresen
2012-01-02 16:42 ` roconnor
2012-01-02 17:10 ` Stefan Thomas
2011-12-31 9:54 ` Joel Joonatan Kaartinen
2011-12-31 17:28 ` Zell Faze
2011-12-29 16:23 ` Gavin Andresen
2011-12-29 17:01 ` roconnor
2011-12-29 17:06 ` Luke-Jr
2011-12-29 18:00 ` Gavin Andresen
2011-12-29 19:54 ` Stefan Thomas
2011-12-29 19:08 ` Pieter Wuille
2011-12-29 21:00 ` Pieter Wuille
2011-12-29 21:31 ` Alan Reiner
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