Nick -
It would be difficult to explain this (Marcus' definition of iteration
vs recursion) to you without teaching you several key computer science
concepts which are not necessarily difficult but are very *specific*.
The first step would be to answer your question of days ago about what a
"System" is. Physicists define System the same way Biologists (or even
Social Scientists) do, just using different components and processes.
It involves the relationship between the "thing" itself (a subset of the
universe) and a model that represents it.
Therein lies two lossy compressions: 1) Reductionism is at best a
convenient approximation... no subset or subsystem is completely
isolated (unless perhaps somehow what is inside a black hole is isolated
from what is outside, but that might be an uninteresting, degenerate
case?); 2) The model is not the thing... we've been all over this,
right? Another lossy compression/projection of reality. oh and a
*third*; 3) We can only measure these quantities to some degree of
precision.
In a system, a simultaneous measure every quantity of every aspect of
the system is it's "state". In practice, we can only measure some of
the quantities to some precision of some of the aspects, and in fact,
that is pretty much what modeling is about... choosing that subset
according to various limited qualities such as what we *can* measure
and with what level of precision and with a goal in mind of answering
specific questions with said model.
At this point, we are confronted with "what means State?"
Your preference for "Analytical Output" vs "State" I think reflects your
attempt to think in terms of the implementation of a model (in a
computer program, or human executed logic/algorithm). The problems with
"Analytical Output" in this context arise from both "Analytical" and
"Output". "Analytical" implies that the only or main value of the
"state" is to do analysis on it. In Marcus example, it's main use is to
feed it right back into an iterated model... no human may ever look at
this "state". "Output" suggests (also) that the state is visible
*outside* the system. While (for analytical purposes) we might choose
to capture a snapshot of the state, it is not an "output", it is just
the STATE of the system (see above).
Marcus point was that in a recursive *program* (roughly a deterministic
implementation rooted in formal symbol processing, of a model of some
"system"), the "system" is nominally subdivided into physical or logical
subsets or "subsystems" and executed *recursively* (to wit, by
subdividing again until an answer can be obtained without further
subdivision). In an iterative *program*, the entire (sub) system model
is executed with initial conditions (state) one time, then the resulting
state of that iteration is used as the initial conditions for the *next*
iteration until some convergence criteria (the state of the system
ceases to change above some epsilon) is met.
I hope this helps... and doesn't muddy the water yet more?
- Steve
I don't know, I don't speak Haskell.
--Doug
On Sat, Apr 13, 2013 at 3:29 PM, Nicholas Thompson
<nickthomp...@earthlink.net <mailto:nickthomp...@earthlink.net>> wrote:
Could be!
Ok. Now that that is behind us, what did the message mean?
N
*From:*Friam [mailto:friam-boun...@redfish.com
<mailto:friam-boun...@redfish.com>] *On Behalf Of *Douglas Roberts
*Sent:* Saturday, April 13, 2013 3:02 PM
*To:* The Friday Morning Applied Complexity Coffee Group
*Subject:* Re: [FRIAM] Tautologies and other forms of circular
reasoning.
Nick,
I surprised that you are not more conversant in computer
languages. You're always, well, niggling about the meaning of
this word, or that one in the context of this or that conversation.
With computer languages, there are very few ambiguities,
contextual or other wise. Kind of like mathematics. For one as
worried as you often appear to be about the true meaning of the
written word, I would have thought that you would positively revel
at the ability to express yourself with nearly absolute crystal
clarity, no ambiguities whatsoever.
Could it be that you seek out the ambiguities that are ever
present in human languages to give yourself something to pounce
upon and worry over, and to provide the opportunity to engage in
nearly endless conversations?
--Doug
On Sat, Apr 13, 2013 at 2:05 PM, Nicholas Thompson
<nickthomp...@earthlink.net <mailto:nickthomp...@earthlink.net>>
wrote:
Can anybody translate this for a non programmer person?
N
-----Original Message-----
From: Friam [mailto:friam-boun...@redfish.com
<mailto:friam-boun...@redfish.com>] On Behalf Of Marcus G.
Daniels
Sent: Saturday, April 13, 2013 1:10 PM
To: friam@redfish.com <mailto:friam@redfish.com>
Subject: Re: [FRIAM] Tautologies and other forms of circular
reasoning.
On 4/12/13 5:40 PM, glen wrote:
> Iteration is most aligned with stateful repetition. Recursion is
most
> aligned with stateless repetition.
Purely functional constructs can capture iteration, though.
$ cat foo.hs
import Control.Monad.State
import Control.Monad.Loops
inc :: State Int Bool
inc = do i <- get
put (i + 1)
return (i < 10)
main = do
putStrLn (show (runState (whileM inc get) 5)) $ ghc --make
foo.hs $ ./foo
([6,7,8,9,10],11)
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/Doug Roberts
d...@parrot-farm.net <mailto:d...@parrot-farm.net>/
/http://parrot-farm.net/Second-Cousins/
/
505-455-7333 <tel:505-455-7333> - Office
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Meets Fridays 9a-11:30 at cafe at St. John's College
to unsubscribe http://redfish.com/mailman/listinfo/friam_redfish.com
--
/Doug Roberts
d...@parrot-farm.net <mailto:d...@parrot-farm.net>/
/http://parrot-farm.net/Second-Cousins/
/
505-455-7333 <tel:505-455-7333> - Office
505-672-8213 <tel:505-672-8213> - Mobile/
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Meets Fridays 9a-11:30 at cafe at St. John's College
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