What's New -  November 2002

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November 25, 2002:  The two of us will each take a 52-card deck, shuffle it thoroughly and place our decks face down on the table.  Now we'll start turning cards face up, one from the top of each deck on each turn.  If we go through the entire deck without two identical cards being turned, player A wins.  If an identical pair is turned, player B wins.  Do you want to be player A or B?   

Some knowledge of the mathematics of Derangements  may help you choose.

We're off to a daughter's house to eat some turkey and all that goes with it for the next few days.  If you live in a country that celebrates Thanksgiving, have a good one.  If you live elsewhere, find something to be thankful for anyway, just on general principle.    See you in December!

A 5x5 board that can be solved in 4 moves*

November 24, 2002:  Here is an update to the Token Flip program  - a game whose objective is to make all tokens white by clicking.  Each token clicked will change the color of that token and those above, below, left and right - if they exist.    A viewer had requested boards larger than the original 4x 4.  This version allows boards up to 7x7. however  the "Auto solve" time gets very large very fast.  Some modifications allow this version to solve 5x5 puzzles in a few minutes.  A general 6x6  game,  say one needing   12 moves to solve, would probably take years even on a fast computer.  We really need heuristics to allow trial moves to be selected intelligently.   I've added a button that will allow random boards with few moves to be generated.  If anyone out he there can figure out how to consistently manually  solve say a 5x5 game requiring  8 or more moves in the minimum number of moves - let me know your "rules" for determining how to move.  *(Col 4, Row 1),(C3,R2),(C4,R2),(C4,R4)

November 21, 2002:  A young friend sent this "Darby Coaster"  the other day as thanks for helping him a little with his Science Fair project.  Actually, he helped me by finding a couple of bugs in the program,   The coaster is cool but I  believe I'll pass on riding the real thing!    Clicking above will download the coaster  - but if you want to see it run and don't have the program yet, it's available from the Roller Coaster Simulator page.

 Have you ever taken so long to find an  answer that by the time you've found it, you've forgotten the original question?   That's the case with today's Set Partitions page and program over the the Math Topics section.   I'm sure I started the investigation in order to help solve some puzzle, but it became a fascinating study on its own.   A set partition is simply a division of a set of distinct things into subsets.  Generating and counting  them involves a couple  more of those numbers with guy's names attached.  

November 20, 2002:  Version 2 of GridQuickSort is available over in the Delphi Techniques section.  A user requested the ability to sort integer fields.  This new demo version  adds a "data type" field to QuickSort permitting columns with  alpha, integer or real data to be sorted.

Deer hunting season is upon us (at least here in Virginia), so  email is slightly backed up. If you sent feedback and requested contact, be patient, I'll get there.    Two are in the freezer so far (deer, not emails),  so the pressure is off -  we'll eat well for the next year.  But the hours spent communing with nature are  restorative,  so I'm still going out - just not so much at 5:30 AM, or in the rain, or when the temperature is in the 20's or when the wind is howling.   :>)

Elizabeth - the reply-to address on your feedback is invalid,  Here's a link to the "Geometry Junkyard" which may provide what you need.  If not, please write again.

November 19, 2002: It's been a while since we posted a real beginner's program.  Here's one that solves a puzzle about the size of Mr. MacGregor's Cabbage Patch.   About 5 lines of code solve the problem and  twenty  lines  display the results.    About normal I guess, 20% doing it and 80% talking about it.

November 16, 2002:   I posted a new version of our most popular program, the Roller Coaster Simulator today.  It  includes a few fixes and enhancements.   I've been working with a young man this week who is using the program as the basis for his 6th grade Science Fair project.    Brendan's great  idea is to compare G forces for circular vs. clothoid loops.   (Clothoid loops are elongated vertically and reduce maximum G force on riders by  taking the cart in a flatter curve when it is going fastest  at the bottom of the loop and  more sharply at the top when it's speed is slowest.)     I added G and Distance columns to the Debug tab data display to help him along a little.    While playing with the program, I decided to improve the accuracy when inserting additional control points into a track  (right click the track to enter design mode and drag, insert, or delete control points).   

November 7, 2002:  

Whew!   Here is the Discrete Event Simulator program - one of those  programs written several years ago that only needed "a little tweaking" to get it ready to post.  That was two weeks ago and has occupied most of my spare time since then.    It simulates "transaction" processing systems that support queuing, including  many of our daily activities from the toll booth to the grocery store to  the gas station, barbershop, and public restroom,  just to name a few.  A big complex topic that I think can be fun to play with, even if you are not a grad student or professor of Mathematics.    Included are several sample cases to give you the idea, and  some simple animation that lets you watch the little customers move through the system.