Delphi For Fun Newsletter #29



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 "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!
 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 non-rectangular 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 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.    



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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