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Re: Re: Return in function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg105720] Re: [mg105682] Re: Return in function
  • From: "David Park" <djmpark at comcast.net>
  • Date: Wed, 16 Dec 2009 06:20:29 -0500 (EST)
  • References: <31131058.1260881796016.JavaMail.root@n11>

There is another use for the terms "predictable" and "unpredictable" in the
theory of computations. A computation is "predictable" if you can derive a
formula for the result without actually going through the entire
computation. I think this relates to NKS and some of the things Stephen
Wolfram is talking about. Much of classical physics concerned predictable
calculations and this has biased us in our view of what is a computation.
Most computations are not predictable, for example: the weather, the
economy, the evolution of society. If you want to know what the result is
you have to accurately simulate every step of the development, or let nature
do the computation and just wait and see.

A good book on this, that might also serve as an independent introduction to
NKS is 'The Lifebox, The Seashell, And The Soul: What Gnarly Computation
Taught Me About Ultimate Reality, The Meaning of Life, And How To Be Happy'
by Rudy Rucker. The book is more serious than the title might indicate.


David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/  

  

From: Bill Rowe [mailto:readnews at sbcglobal.net] 


On 12/14/09 at 12:04 AM, nma at 12000.org (Nasser M. Abbasi) wrote:

>"David Bailey" <dave at removedbailey.co.uk> wrote in message
>news:hg2d7s$j8a$1 at smc.vnet.net...

>>Aren't you being a bit unfair, Daniel has obviously taken time to
>>thin out this example from whatever complicated context he found it
>>in originally - minimal examples of problems often don't make
>>sense:)

>Not only that, but if someone can write code in any language such as
>the output is "unpredictable" then there is something really wrong
>in this picture.

>No one should be able to write code in a well defined language such
>that the output becomes "unpredictable". We are not dealing with the
>heisenberg uncertainty principle here. May be the code is hard to
>understand, ok, but "unpredictable"?

You are being way over simplistic here. Any general purpose
programming language includes the capability of making arbitrary
edits to existing files. That implicitly means I can always
generate code which will cause unpredictable results.

=46urther, a design goal of Mathematica appears to be the ability
to do anything that is possible in Mathematics. Given that goal
and Godel's theorem, it will always be possible to generated
code which has unpredictable results.





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