|My Datafile articles in V26 N1|
Message #2 Posted by Valentin Albillo on 14 Feb 2007, 9:14 a.m.,
in response to message #1 by Giancarlo (Italy)
Why, thank you very much for your extremely kind words ! :-)
I'm very happy that you enjoyed this article so much, as it was a novel approach to show off the HP-35's capabilities in the very best possible light while fully taking into account the existing technology at the time it was released, so that readers could get to really appreciate what it meant to us and to the world as a whole. I'm extremely pleased to see I succeeded as far as you are concerned.
Also, thank you for your heartfelt recommendation of Datafile. As I've said a number of times, it beats me why so many enthusiastic HP fans are so willing to spend large amounts of money for a second or third copy of some HP calc model while thinking nothing of getting an inexpensive subscription to Datafile which can probably afford as much intellectual pleasure related to their HP hobby, if not more, and further helps this very last classic HP fan publication to survive and continue being a most worthwhile treasure trove for all of us who love HP calcs. As they say in some movie, "Hey, MoHP reader, I'm doing my part ! Are you ?" :-)
I'm including here a description of my three articles featured in the current Datafile issue, V26 N1, and cordially invite every reader to consider subscribing to Datafile and have a look at
them. I have plenty of similar materials waiting for your eyes in the
very next issues ! :-)
Long Live the HP-35 !
This 5-page article, belonging to my ongoing "Long Live ..." series,
is intended as a commemorative article for the HP-35's
35th anniversary, and I think you'll agree it's quite an original
approach to it. It does include three sample applications
featuring four small programs, addressing such topics as
root finding and numerical integration, as well as
providing the appropriate historical context and a few
personal anecdotes to spice it all.
Boldly Going ... - Matrix Square Root
This 6-page article is the first of a new series of articles,
the "Boldly Going" series which, as its name implies,
is intended to effectively go "... where no HP calc has gone
before ...", and so they will be dealing with unusually
difficult programming tasks in a straightforward manner,
thus expanding the limits of what you can do with your HP
model and how simply can you do it. For instance,
can you use your little HP calculator to find the matrix
square root of these two neat little matrices
| 56 97 17 89 | | 4 + i 7 + i 3 - i 4 + 2i |
A = | 33 -68 -42 5 |, A = | 6 - i 9 + 4i 8 – 3i 3 – 2i |
| -206 -48 -34 -104 | | 1 + 3i 1 – 2i 4 + 2i 3 + i |
| -39 92 27 30 | | 2 - i 1 + 4i -3 + 4i 1 + i |
that is, to find matrices R so that R*R = A, in each case ?
To provide a taste for the series, this first article deals
with this task of finding the matrix square root of square
matrices. Two full programs are featured: a 7-line subprogram
for the HP-71B which can deal with real- or complex-valued
NxN matrices, and a 45-step routine for the HP-15C which
will find the square root of real-valued matrices up to 4x4. Full examples are provided, with comments and notes, as well as the underlying algorithm.
Small Fry - Primes A'counting
Finally, this 1-page article belongs to the new series
"Small Fry", which is intended to feature very *small* articles
(maximum 1 page), while still keeping all the flavour
and bite of the usual longer ones.
This first article deals with the topic of prime counting,
i.e., finding out how many prime numbers there are up to a
given limit N. For large N, generating all primes up to N and
returning the count is prohibitively expensive in terms
of running time and/or memory usage. What can we do
about it when N goes sky-high (say 1010, 1015, or more) ?
The article features an 8-line user-defined function for the HP-71B to
accomplish the feat very quickly, as well as several comparative
examples against other well-known prime counting procedures.
Best regards from V.