December 5, 2013: Thanksgiving, 2013 is history, the 1st deer is in the freezer, and the front deck has a full load of firewood in preparation for the major ice storm heading our way this weekend. I've filled the free time for the past couple of weeks educating myself about random number generators *RNGs) and how to test them. Thankfully, the result is the Chi-Squared RNG Testing program posted today.
November 24, 2013: ComboTest Version 2.0, our combinatorial calculator; posted today has a minor, but significant, change to allow larger, 64-bit, sample sizes to be analyzed. The change was motivated by request from a college professor simulating a draw of 5 items from a set of 500 values with replacement. There are more that 285 billion ways to do this. The built in Random function in Delphi tops out around 4 billion so I implemented a 64 bit Random Number Generator to allow generating random samples from the 285 billion possibilities. Changes to several DFF library programs were required to implement this.
November 17, 2013: BigIntsTest V2.2 and UBigIntsV4 posted today include the first significant use of features not available in Delphi 7. "Operator overloads" allow us to write arithmetic and comparison operations for big integers much the same as we write for normal integers. The best news is that both old and new versions are supported in single source code images for the unit and the test program.
November 10, 2013: I purchased my XE5 upgrade last week so the learning curve is taking an upward turn. Two postings this week implement the first updates. Testing Delphi Versions now includes the conditional Version names through XE5 and suggests and even better way to automatically change the source code based on compiler version. (Hint: it uses the global constant "computerversion".)
BigIntsTest V2.1 is the big integers test program I was working on to display the internal representation of digits of large integers at the request of a user trying to understand how it works. The download includes a new version the big integers unit which should compile successfully for any Delphi versions after Delphi 5.
November 2, 2013: I received three emails in October which have led me to consider upgrading from Delphi 7 to the current version, Delphi XE5. See 2013 Delphi Upgrade Plans for details.
October 22, 2013: Many have worked on those Logic Puzzles
whose goal is to determine "who sold
what for how much", or "who rode which ride and won what kind of toy".
Solutions are based on
clues and usually include diagonal grids containing true/false sub-grids to enter
help match items across categories. Here's a Logic Grid Print
program which allows the user to print multiple copies of such grids after
entering "Categories" (Names, Rides, Prizes, etc.) and the "Items" within
those categories (Joe, Roy, Sam, etc.). Now you can preserve
those grids in the puzzle magazine for others' use, or create grids for puzzles
which do not include them, or try multiple search paths where a "guess" may be
required to find the solution.
Drop me a line if you would like the text and clues
for this sample puzzle. Have fun!
October 14, 2013: Our ReactionTimes programs measure human response times to various stimuli and save experimental results for further statistical analysis. Changes were implemented today to better handle analysis of results for countries which use comma as a decimal separator in floating point numbers (Europe and others) instead of the decimal point used in North America. ReactionTimes V4.2 and ReactionStats V3.2. should now generate and process response summary files correctly.
September 21, 2013:
My British friend, George, has provided material for
all three projects this
month. Here is a
"Delphi Techniques" program,
Blend Drawing Demo, which explores
his latest problem: semi-transparent shading of a selected quadrant of a
TImage bitmap. Extensions added features to control blend color,
intensity, location, and speed "just for fun".
September 1, 2013: I had an interesting email conversation a few weeks ago with an older gentleman who programs in Delphi as a hobby and was having some trouble with bitmaps and making the mouse interact with a StringGrid. I was able to help him and decided to post this program, String Grids and Bitmaps, in our Delphi Techniques section to pass along what we both learned.
August 26, 2013:
Find All Polygons, Version 3.2
posted today is better than last week's posting at finding all polygons at
a given search level. When I added the figure from our "How Many
Triangles?" program to this program, I realized that some of the interior
nodes (created when interior lines intersect) were not being examined during the
polygon search. The problem is corrected today. The easily checked
polygon counts (the Tennis problem's rectangle counts, the Triangles
problem's triangle counts, and the the primitive counts for any figure are now
correct. (Total rectangle and triangle counts are found by limiting "Max
Search Depth" values to 5 and 4 respectively.)
August 22, 2013:
After a month of on-and-off effort, here is
Find All Polygons, a program to
look for polygons, closed figures formed from connected straight
line segments. According to Wikipedia, "Polygon" is derived from Greek
with literal meaning "many corners". Typically, but not always,
the number of corners, (vertices), equals the number sides (edges). I
learned much about them in the course of writing this program including the
many ways that arbitrary closed sets of of lines may not be
valid polygons. The program analyzes several different sample figures
including one from which several hundred polygons can be selected.
Needless to say, I have not examined all of them so there still may be
polygons missed or non-polygons selected. Let me know if you find
August 13, 2013: The Challenging Math Teasers program posted today implements three problems of the 100 presented in the "Challenging Mathematical Teasers" book by J.A.H. Hunter and published by Dover Publications. The puzzles generally require math techniques beyond simply solving an algebraic equation or two. The three presented here were chosen randomly are easily amenable to programmed solutions (and have relatively short descriptions :>). By the way, the above book link to Amazon offers a number of good used copies for $0.01 + $3.99 shipping, if you reside in the U.S. and act quickly.
The program is a one day effort while taking a break from the "Find All Polygons" program I have been wrestling with for the past two weeks. Who knew polygons could be so hard to find?
I placed this program in the Math Topics section of DFF but also indexed it under Delphi Techniques and Beginners categories since it does illustrate some useful number manipulation techniques with less than 20 source code statements to handle each of the 3 problem buttons.
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