Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!aioe.org!feeder.news-service.com!newsfeed.xs4all.nl!newsfeed6.news.xs4all.nl!xs4all!post.news.xs4all.nl!not-for-mail
Return-Path: <python-python-list@m.gmane.org>
X-Original-To: python-list@python.org
Delivered-To: python-list@mail.python.org
X-Spam-Status: OK 0.000
X-Spam-Evidence: '*H*': 1.00; '*S*': 0.00; 'fine,': 0.07; 'indeed,': 0.07; 'infinite': 0.07; 'mode,': 0.07; 'pretend': 0.07; 'terry': 0.07; 'python': 0.07; 'correct.': 0.09; 'default)': 0.09; 'generators': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:80.91.229.12': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'received:lo.gmane.org': 0.09; 'pm,': 0.11; '>>>': 0.12; 'output': 0.12; 'am,': 0.14; 'extension': 0.14; 'wrote:': 0.14; 'defined': 0.15; 'iterators,': 0.16; 'lambda': 0.16; 'reedy': 0.16; 'subject:versus': 0.16; 'summary,': 0.16; 'algorithm': 0.16; 'input': 0.18; 'obviously': 0.20; 'tue,': 0.20; 'jan': 0.22; 'header:In-Reply-To:1': 0.22; '(and': 0.22; 'reference.': 0.23; "didn't": 0.25; 'says': 0.25; 'function': 0.27; 'url:edu': 0.28; 'problem': 0.29; '(as': 0.29; 'mode': 0.29; 'universal': 0.29; 'operating': 0.30; 'least': 0.30; 'implement': 0.30; 'finite': 0.31; 'turns': 0.31; 'it.': 0.31; 'to:addr:python- list': 0.32; 'thank': 0.32; 'etc)': 0.33; 'header:X-Complaints- To:1': 0.34; 'change': 0.34; 'describe': 0.35; 'header:User- Agent:1': 0.35; 'long.': 0.35; 'subject:software': 0.35; 'machine': 0.37; 'apr': 0.38; 'but': 0.38; 'pretty': 0.38; 'received:org': 0.38; 'authors': 0.39; 'machines': 0.39; 'to:addr:python.org': 0.39; 'header:Mime-Version:1': 0.39; 'except': 0.39; 'header:Received:5': 0.40; 'domain': 0.40; '2011': 0.62; 'interest': 0.65; 'believe': 0.66; 'subject:Free': 0.72; 'papers': 0.74; '10:32': 0.91; 'calculus': 0.91; 'subject,': 0.91
X-Injected-Via-Gmane: http://gmane.org/
To: python-list@python.org
From: Terry Reedy <tjreedy@udel.edu>
Subject: Re: Free software versus software idea patents
Date: Tue, 12 Apr 2011 15:39:05 -0400
References: <mailman.65.1302065189.9059.python-list@python.org>	<t7Vmp.7632$zn.3197@newsfe19.iad>	<mailman.72.1302078388.9059.python-list@python.org>	<4d9c5ca5$0$29991$c3e8da3$5496439d@news.astraweb.com>	<87tyebf3r3.fsf_-_@benfinney.id.au>	<_Abnp.8356$zn.729@newsfe19.iad>	<4d9d6587$0$29992$c3e8da3$5496439d@news.astraweb.com>	<OHlnp.10535$g56.5872@newsfe04.iad>	<mailman.121.1302206148.9059.python-list@python.org>	<__top.14604$zn.8052@newsfe19.iad>	<mailman.209.1302508440.9059.python-list@python.org>	<8d9a097d-1160-4131-8bde-65e8e2ff3240@k5g2000yqj.googlegroups.com>	<io22aq$jdb$1@dough.gmane.org> <BANLkTinLKsQggjVsHgeF=vsA-YVd=eQdFw@mail.gmail.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
X-Gmane-NNTP-Posting-Host: rain.gmane.org
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.15) Gecko/20110303 Lightning/1.0b2 Thunderbird/3.1.9
In-Reply-To: <BANLkTinLKsQggjVsHgeF=vsA-YVd=eQdFw@mail.gmail.com>
X-BeenThere: python-list@python.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe: <http://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive: <http://mail.python.org/pipermail/python-list>
List-Post: <mailto:python-list@python.org>
List-Help: <mailto:python-list-request@python.org?subject=help>
List-Subscribe: <http://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups: comp.lang.python
Message-ID: <mailman.280.1302637159.9059.python-list@python.org>
Lines: 41
NNTP-Posting-Host: 82.94.164.166
X-Trace: 1302637159 news.xs4all.nl 32470 [::ffff:82.94.164.166]:36705
X-Complaints-To: abuse@xs4all.nl
Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:3082

On 4/12/2011 2:44 PM, Dan Stromberg wrote:
> On Tue, Apr 12, 2011 at 10:32 AM, Terry Reedy<tjreedy@udel.edu>  wrote:
>> On 4/11/2011 4:36 AM, rusi wrote:
>>
>>> http://www.cse.uconn.edu/~dqg/papers/cie05.pdf
>>>
>>> may be of interest (and also other papers of Peter Wegner questioning
>>> the universality of Turing machines lambda calculus etc)
>>
>> Thank you for that reference. In summary, it says that while Turing machine
>> are universal for finite function calculations, infinite interactive
>> processes are not (finite) function calculations, and therefore need an
>> extension to TMs. This is pretty obviously correct.
>>
>> Python iterators, and especially generators, implement the extension that
>> the authors call 'persistent Turing machines' (PTMs, section 6.2), except
>> that iterators (and generators by default) operate in 'pull' mode, while
>> they describe PTMs as operating in 'push' mode (as with generator.send()).
>
> I didn't read the paper,

If you are interested in the subject, I recommend it. It is pretty clear 
and not long.

> but I believe Turing Machines are infinite.

An 'effective' algorithm/TM turns a finite input into a finite output in 
a finite time, without outside intervention, and then halts. The Halting 
Problem arose because of the requirement that effective machines halt, 
and indeed, a particular proof that a particular algorithm halts on all 
inputs in the defined domain is part of the proof that it is 'correct'.

> Interactive processes don't seem, at least to me, to change the
> applicability of Turing Machines - you merely pretend you have a bunch
> of squares preinitialized with your various inputs.  If you have an
> infinite number of inputs, that's fine, you can have them with a
> preinitialized turing machine.

-- 
Terry Jan Reedy