[q-lang-users] [Fwd: Why cant I differentiate]

[Albert G. <Dr....@t-...>]

Hi all,

this is a post by Koray Erkan which, for some reason we both don't
understand, bounced back from the sf.net mailing list server even though
he's subscribed to the list, so I'm posting it on his behalf. Until
Koray gets his mailing problems sorted out, please be so kind to cc your
replies to ke-1256 (at) isnet.net.tr. Thanks.

Albert

-------- Original Message --------
Subject: Why cant I differentiate
Date: Sun, 3 Jun 2007 11:21:39 +0300
From: Koray Erkan <ke...@is...>
To: <q-l...@li...>

<div class="moz-text-flowed" style="font-family: -moz-fixed">Hi --

I'm very new to Q. I've copied the following bits of code from a white
paper ("Why Functional Programming Matters") - making a few very minor
changes to meet Q's syntax requirements as needed. It doesn't run, and
my hunch is there's something wrong with the "repeat" bit of it. I know
it returns and infinite list, but I've tried using an accessor (i.e.
"(list)! <index-id>") to get a single returned value which in turn
didn't work.

I'm probably trying to fit square pegs into round holes somewhere, but
as I don't have the time to check every option, I thought of consulting
the mailing list. Your help will be appreciated.

--

easydiff F X H
   = (F (X+H) - F X) / H;

differentiate H0 F X
   = map (easydiff F X) (repeat halve H0);

halve X
   = X/2;

elimerror N (cons A (cons B Rest))
   = cons ((B*(2^N)-A)/(2^N-1)) (elimerror N (cons B Rest));

order (cons A (cons B (cons C Rest)))
   = round (log2 ((A-C)/(B-C) - 1));

improve S
   = elimerror (order S) S;

super S
   = map second (repeat improve S);

second (cons A (cons B Rest))
   = B;

--

BTW Is there a way to "step" through the code ? Dijkstra would probably
write another paper how stepping through code "maimes/cripples" the mind
forever (good old Dijkstra, much as respect him, he can't seem to get
through a paper without somebody being crippled or a methodology that
would require a gazillion-dollar industry change isn't suggested ;-D),
but as I don't have a 170 IQ (a fact which Dijkstra and his ilk
frequently forget in dealing with these matters), I am not able to
shuffle and update 37 variables simultaneously in my head or eat tensor
calculus formulae for breakfast. To make a loose analogy with a
"disabled" person, a wheel-chair may appear "crippling" to someone
perfectly able to walk (say Dijkstra), but to someone who has lost his
walking ability, it is *liberating*. Same thing with IQ and
computer-interaction: No matter what our genius (elite) computer
scientists say, a debugger that can step through code is liberating - at
least to those of us crippled with less IQ.


Cheers
-- Koray


</div>

-- 
Dr. Albert Gr"af
Dept. of Music-Informatics, University of Mainz, Germany
Email:  Dr....@t-..., ag...@mu...
WWW:    http://www.musikinformatik.uni-mainz.de/ag