The message below is being cross-posted from the LogoForum. Please
reply here at comp.lang.logo and it will be cross-posted back to the
LogoForum. The original author of this message is
gene_sullivan@[EMAIL PROTECTED]
In LogoForum@[EMAIL PROTECTED]
Pavel Boytchev <pavel@[EMAIL PROTECTED]
> wrote:
>
> logo_programmer wrote:
>> --- In LogoForum@[EMAIL PROTECTED]
"jotape1960" <jotape1960@[EMAIL PROTECTED]
> wrote:
>> Too many iteration-loving Comp-Sci types still
>> disparage recursion, and languages which
>> either support or promote recursion.
>
>
> May be it is also a matter of personal
> preferences and a matter how data are
> represented (i.e. the algorithm is not the only
> factor!).
Sure. Varying from person to person.
Though I and a friend have swapped horror stories
of how various `programming' and `Comp Sci' professors
have disparaged recursion as terra incognita ... to
be avoided for fear of .... well just don't do it.
>
> For example, for linear iteration over an array
> I'd prefer to use REPEAT or FOR (or WHILE if the
> number of iterations is unknown in advance).
> However, for non-linear iteration, like
> traversing a tree or a graph, I'd definitely
> prefer a recursive approach.
Sure.
I had classes in college in both data structures
and algorithms ... as separate classes.
I recall how some Austrailian Aboriginies
(EG not Bulgarian Aborigionies) were tested
by clinical psycologists to see if they could
match up some items ... the kind of stuff
kids in kindergarden are compelled to do.
Rather than to group all the eating utinsils
together and all the foods together, they
matched the eating utinsil with the type
of food they would use it on/with.
I'm with the Abos on this one.
It makes a hell of lot more sense to present
algorithms and the data stuctures they are used
by/with togeher as a synergy than to play out some
Categorical discrimination game leaving the
`student' not able to see the forest for the
trees.
>
> There are also heterogeneous loops. The parsing
> phase of Lhogho (and Elica) uses both recursion
> and iteration; and they are interlaced.
Sure. Underneath ... out of sight and mind for the
average user of Logo.
>
> I'm curious as to what is the situation if we go
> outside Logo and CS.
> Is
> the Nature recursive or iterative by nature?
Yes.
Sorry ;-) Couldn't resist.
> Or maybe it is both of them? Or none?
You bite off quite a mouthful with `Nature', don't you?
And when did the minds of men accept nature as they find it?
We can't seem to stop using mathematical precepts and concepts
to describe It.
So, it would be no mystery to me if the minds of men
`projected onto' `Nature'/Universe/Cosmos/Reality both
`interation' and `recursion'.
> Is DNA replication pure linear iteration?
Is ... is and only is?
Protien folding seems to `be' trans-linear
Though a linear pattern may be used as a template
the strand of protein-in-progress gets looped back
on itself to form 2D and 3D shapes from the 1D
`string' of RNA replicated from DNA, doesn't it?
> What are fractals?
To whom?
An artist?
A mathamatician?
A child?
An adult?
> While looking at a Mandelbrot
> fractal the image appears to be recursive, while
> the drawing algorithm is purely iterative.
Excellent point.
> A mountain skyline looks chaotic, but can be
> generated recursively.
Sure. Thus allowing fractal compression to be
used effectivly for representing mountain ranges.
BTW. If one thinks about it, circles are typically
drawn in Logo as `fractals'.
If one regards the problem of measuring costlines
and perimeters as fundamental to fractals, then
sides of any regular polygon used to represent a
portion of the circumference of a circle ARE being
used as in/with fractals, are they not?
Every regular polygon approximates a circle `fractally',
it seems.
Though I may have violated a few notions of what
mathematicians `know' about fractals.
I really don't know.
Its fun for me to think about polygons this way though.
And what about real-world circles ... things made of
of atoms? If one plays connect-the-dots with atoms
one ALWAYS ends up with a `perimeter' rather than
a `circumference'. A friend and I were playing
with the concept of fractal circumference and
Fractal Pi a few years ago. I'm not sure we
came up with any break through s. But the re-framing
of the conventional `circle' and `circumference'
as-of `fractal' approximations allows one to think about
things in another way.
Cheers!
Gene
__._,_.___
LogoForum messages are archived at:
http://groups.yahoo.com/group/LogoForum
|
