Delphi For Fun Newsletter #29
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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 "T-Shirt" 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
Runge-Kutta 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, spring-mass 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
non-rectangular things (ellipses and letters and a little
walking man) move smoothly and quickly across the
screen. Some of the mysteries are even solved!
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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 Runge-Kutta 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.
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Gary Darby
http://delphiforfun.org
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