What's New -  August 2009

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August 24, 2009:  A new version today of our GridQuickSort program in the Delphi Techniques section of DFF.  A viewer had asked about multi-column StringGrid sorting the other day which led me to learn that sort algorithms can be classified as "stable" or "unstable" depending on whether the preserve the input order when equal keys are encountered.  With a stable sort, multiple columns may be sorted by running multiple single column sorts from the minor keys to the major key.  Quick sort turns out to be unstable, as is Shell sort, another efficient sorting method.  Merge sort however fills the bill as GridQuickSort, Version 3 illustrates.

August 19, 2009:

Puzzle #9 in figure set Medium.tan,  - Oops!

A sharp user from Portugal caught a design problem with our Tangram program.  The source of the original design and the puzzles were from Dr. Mark Overmars, a professor at the University of Utrecht in the Netherlands who's lucky enough to make his living by teaching, designing, and, I suppose, playing, computer based games.  .  His version of Tangram was originally freeware but has since gone commercial.  The puzzles that were part of that package have a slight problem that allows certain puzzles to have all of the pieces place on them with no overlaps, but with a little white space left over!.  Tangram Version 4 posted today, kind of addresses the issue by at least recognizing and notifying the user that this is not the desired solution.   

August 12, 2009:

I wrote a version of a popular game called Sokoban this week, not that the world needs another one.   I'm considering tackling a "solver" for this simple but challenging game and decided I needed a simple version as a solver test bed.  I call mine Simple Sokoban, but even a simple version required a 500  lines of code though and kept me out of trouble for another week.  

<==== Simple case (Even with only 4 boxes to place on 4 targets, they get harder fast!)
 

August 5, 2009:  Programming productivity is being impacted these days by garden chores, a new WII  console with balance board, a new kitten in the house, and Sokoban. 

 If you don't know about Sokoban puzzles, check it out at Wikipedia.  A Delphi user is developing a manual play version wrote asking a question  which led to my finding an online version at LetsLogic.com.  The site requires registration, but the fellow who runs it is just a lover of the game and has collected thousands of addictive puzzles.  

I did decide to post a simple Count  Clicks Demo program I wrote today for a for a new Delphi user. As the name implies, it counts and displays the number of times that a button has been clicked.   Only 9 lines of user written code, but three event exit methods might make it worthwhile for beginners.