## Delphi For Fun Newsletter #3

[Home]

Sunday Oct 8, 2000

Gud-dai!

How do you write the Australian pronunciation of "good day"?  The Olympics are over, but I've been communicating this week with a tutor who lives in New Zealand.   He writes like would speak with a similar accent.  He has provided some good feedback on first versions of the Scientific Grapher program.   I decided to go ahead and post the source code for this program, even though it won't compile on Delphi Standard.  It requires a version with the TChart charting component included in Delphi 5 Professional and Enterprise versions for sure, perhaps Delphi 4.

The executable version if Sci-Grapher is available for download though.  It will run on any Win32 system (Win 95 and above).

Programs about two other topics were posted this week: Tetrahedrons and Permutations.

Tetrahedrons are triangular pyramids.  If you place three marbles on a flat surface all touching each other and place a 4th marble on top, you have made a tetrahedron.  The next larger size would have 6 marbles on the bottom, then 3 in a second layer and 1 on top for a total of 10.   If you continue building larger pyramids this way, there is only one other whose total number of marbles is the square of an integer.  We'll consider 1 to be the smallest with total of 1=1X1 marbles, the 4 marble pyramid is the second (4=2X2).   The program Triangular Pyramids finds the 3rd.

The total number in these pyramids form a  sequence of tetrahedral numbers with many interesting properties (for example they always occur as 3 even numbers followed by an odd number).  The number of marbles in each layer form a sequence of triangular numbers, also very interesting.   There are only 5 numbers that are both tetrahedral and triangular.

Three programs about permutations were posted.  Permutations are rearrangements of things.  The letters ABC can be rearranged in 6 ways - there are 6 permutations of 3 things.    Permutes1 introduces the topic and displays all permutations for a number that you enter.  (Well, within reason - there are over 3 1/2 million ways to arrange 10 things.  I don't think the program would print them all.)    Rotating Sums is a program that solves a particular problem for the digits 1-9 arranged in a 3X3 grid.  I'll let you go to the website for details.  Alphametics solves word arithmetic problems like ADAM+AND+EVE=MOVED where each letter stands for a different digit.

That's it for this week.  We had our first snow flurries this morning, so I guess I had better go start getting up our winter's supply of wood.

700 viewers to date.

____________________________
Gary Darby
http://www.delphiforfun.org
------------------------------------------

If you find something you love doing as you're growing up, look hard to see if you can make a living at it instead of giving it up for something more sensible. -- Jennifer Lamb (stuntwoman)