What's New -  April, 2005




April 29, 2005: I created a Simple Backtracking Demo on the Beginners page this morning in response to an inquiry from a student.  There are already several examples on the website, but I enjoy doing one from scratch because the probability of success is high - it's kind of a test to see if Alzheimer's has kicked yet.  So far, so good.     

April 24, 2005:  A big "thank you" to all those who use the Amazon link at the bottom left of our home  page to place your orders.  Today I received a $16.16 Amazon Gift Certificate for your purchases so far this  year.  That covers my expenses for a month!    On average I seem to get about  2.5% of what you spend, so cumulatively, you have spent a hunk of change!  Thanks again.   

April 22, 2005:  Version 2 of the Mirrored Text Test program was posted today.  It adds another piece of the solution for a real teleprompter application: synchronized speed-controlled auto-scrolling of the input and mirrored text.     .

April 19, 2005:  

Two friends who have an eight-quart jug of water wish to share it evenly. They also have two empty jars, one holding five quarts, the other three. How can they each measure exactly 4 quarts of water?  

Here's our version of the classic "Water Jug Problem" which will let you try your hand at solving this problem, and many others.  If you have trouble finding the 7 required moves, a button click will show you how! 

April 15, 2005:   

 Inverted Text,     Mirror text,     Or Both?

A fellow wrote the other day asking about "mirrored" text for a teleprompter application he was working on.  I started out to modify an Inverted Text demo program over in Delphi Techniques,   but ended up with an entirely new application.  The TestMirroredText program described here uses the  Copyrect procedure to copy text from one canvas to another.  It turns out that it's smart enough to handle cases where the left and right (or top & bottom, or both sets of) coordinates are reversed.  the result is a fairly fast way to flip or mirror, or rotate an image.  Along the way, I learned a few more things about re-justifying TMemo lines and setting margins.          

April 14, 2005:  Here is the next version of Cutlist, Version 2.1.3.  Cutlist is a woodworker helper program which displays the optimal layout for a set of parts from a given set of material.  This version adds the ability to specify a  "duplicate count" to simplify entering multiple parts with the same dimension in a project.   There's one more pending request - ability to zoom the displayed results across multiple pages for better readability for large projects.    Those woodworker guys are really using this!  I'll try to get to it next week. 

April 13, 2005:  I corrected a small problem in UBigIntsV2, our large integer arithmetic unit the other day.  (Multiplication by a negative 64 bit integers ignored the sign).  Rather than update all six programs which use this unit, it was relocated to the DFF Library file.  So these programs will now need access to the library in order to recompile successfully:  Big Integer test,    Multiple Length Long Division, Pell's Equation and Continued Fractions.   Big Floating Point Arithmetic,   Big Combos ,   T-Shirt XXL  (Armstrong numbers).   The error did not affect any of these programs, so no need to re-download executables, but if you have the source code, it would be a good idea to download the Library file to get the latest code.

April 12, 2005:  Completed Project Euler!  Yesterday I finished the last of the 95 programs in this challenging set of programming projects.   5 of the 18 who have completed all the problems are  Delphi programmers.  One of them, a non-native English speaker, who also recently made it, expressed the satisfaction best.  He wrote "I am happy like a child!".   After working five months on the last problem (#60), I can only echo that sentiment and say "Me too!"    

April 11, 2005:  I sent DFF Newsletter #39 last Friday so if you think you are subscribed and did not received one, you are one of the 71 subscribers with an inactive account, full mailbox, unknown user, or whose ISP thinks that DFF sends spam.     While watching Tiger win  the Master's Golf Tournament yesterday, I wrote a program to help me update the subscribers list.   Text File Update  processes a list of bad email addresses against a total subscriber list and deletes the matches.   While at, it I included a few extra goodies like options to add unmatched transactions, delete duplicate master records.  ignore or consider capitalization when matching, ignore leading trailing blanks, etc.   For programmers there's  version 1 of a TSyncMemo class that allows three lists (Master recs., Update recs., Action taken) to be scrolled synchronously from a single scroll bar.   

April 6, 2005: 

Here's Version 2  of our Solar Position program which calculates sunrise & sunset times, well as the position of the sun any given time for any location on earth.  "Analemma" plots are also produced.  An Analemma is  the figure traced in a year if the shadow tip of a fixed stick were plotted at the same time each day for a year.

 There were a few minor bugs to correct, plus a few user suggested enhancements, plus a new experimental solar position plot  (June 21 solar path at 30 North shown at left)  

April 5, 2005:  An enhanced version of the TComboset unit was posted today as the 2nd addition to our DFF  Library.  Thanks to Charles Doumar for the added functions - even if I don't know why or when to use combinations in Colexicographic order.   Here's a link to the Comboset test Program.    It is a compatible replacement for our  Combo unit which is used in many DFF programs.    

April 1, 2005:  Many themes and shared borders are missing in the Programs section today.  I would suspect an April  Fool's day joke, except that I was seeing "Insufficient Disk Space on Server" errors earlier today while doing a minor update.  We'll see if it magically fixes itself by tomorrow.