Delphi For Fun Newsletter #29[Home]
Friday, October
4, 2002
It's fall and
we're seeing the first signs that winter is on the way.
The last hummingbird abandoned us a couple weeks ago to
head for warmer climes . The birches, Virginia creeper and
Sassafras are all
coloring up and the maples are thinking about donning their new red fall
coats. About 3/4 of our winter wood supply is cut,
split and stacked down by the shop. Each year I think
that this is the year to buy a powered wood splitter, but
then I think about the benefits of exercise (and what a nice
computer upgrade the money would buy).
Two thirds of the kids
and grandkids are coming for a fall visit next week, so I
decided to get a
newsletter out to the viewers who like occasional reminders of
what is new here at DFF .
The list server at our host site has been down for several
days, so I had to reconstruct the distribution list and
I'm trying a new mail distribution program. If things
don't look right or you don't get this (:>), let me know.
Most of the programs in the past six weeks have had a
"simulation" or "Delphi techniques" flavor. I did get a
neat "Chessboard Fallacy" program posted a couple of days
ago. Yesterday I decided to take a look at download
statistics from the DelphiForFun log files that I've been
accumulating. We passed 25,000 home page visitors this
week and there have been more than 65,000 downloads in the
past 11 months! I posted a "Top 25 Downloads" page for
those who may be interested.
Here are the rest of the "What's
New" items
since last time:
August 25, 2002: I've been working on Linkages, a mechanical linkages simulator program this week, but it's going to take at least another week to get anything even close to working. In the meantime here are a couple of others of the "Can You Find?" or "TShirt" variety that somehow had never gotten posted. Pandigital Numbers introduces that topic and asks for the smallest pandigital that is a perfect square and the smallest number that, together with its square, contains all of the digits from 1 through 9. Remainder of 1 looks for, (and finds), the smallest multiple of 13 that leaves a remainder of 1 when divided by integers 2 through 12. We do this in a couple of ways and compare run times measured in microseconds. (The smart way is about 100 times faster.)
August
30, 2002: We were sidetracked again this week
by an interesting project  converting a differential
equation solver to Delphi. Don't let your eyes glaze
over just yet. There are lot's of academicians to
supply us with the equations describing how things
work. We just need to be able to convert them to
numbers we can print, plot or otherwise play with.
Here's a
RungeKutta program over in Math Topics with
procedures and test cases for solving Second Order
Ordinary Differential Equations with Known Initial
Conditions. Machines that follow Newton's Laws of
Motion including projectiles, rolling or sliding
objects, pendulums, springmass systems, etc. can be
described with equations of this type. Useful indeed
for those of us interested in computer simulations of
the real world.
September
8, 2002: I finished working on some
Sprite Animation demo programs this week and posted
them over in the Delphi Techniques section. Really just
an investigation to the mysteries of making
nonrectangular things (ellipses and letters and a little
walking man) move smoothly and quickly across the
screen. Some of the mysteries are even solved!
September
11, 2002: While working on the Sprite Animation
program, I had to study up on Mask drawing, the tricky way
that programs can nicely put a nonrectangular image over
another image using a system that only knows how to draw
rectangles (i.e. Windows).
Here's a
Mask Drawing description and demo
program showing how the trick is
performed.
September 16, 2002: Occasionally it's convenient to identify which version of Delphi is being used to compile a program. Borland predefines conditional symbols identifying Delphi versions but the values are not very well documented. I just spent a couple of hours tracking them down so here's a Testing Delphi Versions page to save doing it again.
September 21, 2002: Here's another program, Pendulums Simple and Otherwise, written to exercise the RungeKutta differential equation solver posted a couple of weeks ago. This version explores and animates three pendulum variations  Simple, Double, and Damped Forced. Interesting to play with, even if you're not into that higher math stuff.
September 28, 2002: I ran across this experiment the other day which uses playing cards to start us thinking about the Number of Divisors of positive integers. This simple little program uses card images and flips them for you in case you have mislaid your real deck.
October 1, 2002:
The Chessboard Fallacy program tells you how to cut a chessboard and rearrange the pieces in such a way that the number of squares is reduced from 64 to 63. Unlike some cutting puzzles, these pieces do not cheat on the angles  the pieces will fit exactly. Of course there are many ways to cheat....
October 2, 2002: I wrote a little program today that analyzes DelphiForFun log files and extracts program download statistics. Here's a page of 'Top 25 Program Downloads " for the past 11 months, 30 days and 7 days. There's still some work to do automate generation of the tables but the numbers are kind of interesting.
____________________
Gary Darby
"You cannot create an idea: it just happens  and
you have to be on the alert to seize it when it does
happen. " 
H.E.Dudeney, Mathematician & Puzzleist
"The Bible says, 'If you wish to find, you must
search.' I believe that is true, rarely does a good idea
interrupt you.  Jim Rohn
"I am enough of an artist to draw freely upon my
imagination. Imagination is more important than
knowledge. Knowledge is limited. Imagination encircles
the world."  Albert Einstein
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