Both my vocation and avocation are computer programming. Here's my resumé.

Once I was involved in the IBM add-on memory industry. Here's a detailed discussion of an interesting bug from those days.

When I was first learning to create html pages, for some reason I chose to build a list of great mathematicians as a practice page, even though I wasn't qualified to make such a list without a lot of advice. Since then I've invested a lot of time reading mathematical histories and biographies and revising the page. I'm proud of it now: please read it! (With 50 mini-biographies, the single page has now grown to over 100 kbytes. With today's fast speeds, I suppose this is not a problem, but please tell me if I'm wrong!)

• My List of the Greatest Mathematicians

I like composing a variety of puzzles:

• Figure out this Family Tree.
• Guess what's special about three poems I wrote.
• Here are some very hard Nurikabe puzzles.

I'm also interested in Games and Gambling. Here are some comments on Connect-Four.

Signal Processing on a Hexagon Grid

One of my research interests is the hexagon grid to facilitate machine vision and other 2-D signal processing tasks. The advantages of that grid over the standard square grid have been known for a long time, but it is seldom used. (I guess the prevalance of the square grid shouldn't be surprising, considering that the advantages of Unix are even more clearcut, but MicroSoft Windows has overwhelmed the planet.)

Here is one of my research papers on the topic of ``Filter Banks for the Hexagon Grid''.

Lessons in Expert Programming (C Language)

I've decided to try my hand at offering software tips. Wish me luck !!

Only a few chapters are currently on-line. I'll post more if there's interest.

• Preface: Programming as Poetry.
   
• Lesson 1: Choices for Coding
• Lesson 2: Simplicity.
• Lesson 3: Simplicity (cont'd).
• Lesson 4: Simplicity (cont'd).
• Lesson 5: Simplicity (cont'd).
• Lesson 6: Working from Specifics.
• Lesson 7: Processes and Computation
• Lesson 8: Data Structures.
• Lesson 9: Control Mechanisms.
• Lesson 10: Programming tactics.
• Lesson 11: Focus on Information.
• Lesson 12: Advanced Exercises.
• Appendix M: Memory Requirements.

The textbook is free. If that makes you feel guilty, contact me for Pay-Pal number. If that makes you feel hilarious, sorry.

Eventually I'll create a webpage summarizing comments. For now:
 
> I don't like K&R-style function prototypes.
In Lesson 1 I explain why strong typing is a mixed blessing.
 
> My non-gnu compiler does not accept `long long'
Sorry. If you can't think of a work-around, try an easier exercise.
 
> Those who can't, teach.
Even pejorative comments are welcome, but please attach your own exercise solutions to verify we're playing in the same league.
 
> I didn't think it was so bad, and parts were almost well-written.
Flattery? Yes, that works.

Recently (November 2008) I posted some hash table code here, that I hope others will find useful. Files are:

• Text files
  • Readme -- discussion
  • License -- conditions of use
• General source files
  • makefile
  • bitaccess.h
  • genhash.h
  • pharith.c
• Files for cuckoo hash
  • cuckoo.c
  • cuckhash.h
• Files for tight hash
  • tightch.c
  • tighthash.h
  • genparms.c
• Sample applications
  • pegplay.c
  • wcounter.c
• Compressed archives
  • hashing.zip
  • bible.zip

hashing.zip is simply a compressed archive of the first 13 files. (Also download and unzip bible.zip to get the test file specified in the makefile for wcounter.) I never know whether to add the end-of-line carriage-returns needed by Windows. Here, the individual files have them, but not the elements of the archive. (This November release is the very first: check back later for improved code or documentation.)

A few other snippets of my code are also posted here. Please tell me if you find any useful:

• cf.c -- show real number as continued fraction.
• gencombo.c -- subroutines to generate combinations.
• sofa.c -- fast operations on compressed sparse bitfields.
• bship.c -- generate battleship solitaire puzzles.
• prime.c -- print a list of prime numbers.
• randsub.c -- interface to random().
• holdodds.c -- show poker odds.
• timelimit.c -- run Unix command with time limit.
• sumfact.c -- sum a number's factors, iterate.
• earthdist.c -- show distance between two points on Earth.

I've just placed a few chapters on-line so far, but some of the other programming examples are available. These are mostly simple short programs with interesting or instructive features.

In (rough) order of increasing complexity.

• (from Lesson 5) Print a simple statistic about an acyclic digraph.
• (from Lesson 5) Computer plays Waldo's Nim (against teletype).
• (from Lesson 3) A system of hash tables to find the Shortest path between two game positions.
• (from Lesson 9) A program to solve Double Dummy Bridge Problems, and some comments on the use of ``goto.''
• A comparison of the Double Dummy Bridge Program with a ``structured'' alternative.
• (from Lesson 7) Finding the optimal solution to Ginnow's Sieve.
• (from Lesson 11) Text compression and decompression with the Burrows-Wheeler Transform.