Software

There is a Romanian translation courtesy of Science Spaces, a Polish translation coutesy of Valeria Aleksandrova, a Kazakh translation courtesy of John Vorohovsky, and a Russian translation courtesy of Nikolay Pershikov.

• Code for the complex arcsine, arccosine and arctangent functions
• Xkbset: a program to set XKB controls
• Fluids Programs
• AccessX for X Window
• Natural Math
• Polyomino Puzzles
• The Spherical Package
• The "Fast Exact Closure" Package

Code for the complex arcsine, arccosine and arctangent functions

The code is available at http://people.freebsd.org/~stephen/ in the files catrig.c, catrigf.c, catrigl.c. Tests indicate that both the real and imaginary parts of the results are good to within 4 ULP (units in the last place). They are certainly much more accurate than the current implementations in glibc or NetBSD. The code catrig.c is fully commented, and the code catrigf.c and catrigl.c are float and long double (80 bit and 128 bit) versions respectively. (The float version has occasionally given results whose accuracy is slightly worse than 4 ULP.) See https://wiki.freebsd.org/Numerics for progress on numerics in FreeBSD.

The algorithm in the paper by Hull, Fairgrieve and Tang is also used in the Boost libraries: http://www.boost.org/doc/libs/1_53_0/boost/math/complex/asin.hpp. Their implementation is more faithful to the original algorithm then my code. The Boost libraries also contain code for atanh and acos. The last two algorithms needed fixes to be accurate in some edge cases: see https://svn.boost.org/trac/boost/ticket/7290 and https://svn.boost.org/trac/boost/ticket/7291.

Xkbset

You may also like to look at other similar programs:

• the program xkbctrl at ftp://ftp.freebsd.org/pub/FreeBSD/ports/distfiles/xkbctrl/.

Fluids Programs

• The screensaver xlockmore contains the mode euler2d, which simulates the 2D Euler equation. Use version 4.17 or above (but version 4.18 contains significant optimizations). It may be obtained from here or here. This has now also been incorporated into the xscreensaver program.
  

• I have written a few programs to simulate the Navier-Stokes equations with periodic boundar conditions. They make great use of the Fast Fourier Transform package fftw. For displaying, they make use of the OpenGL protocol - I use the Mesa package. They are available here.

AccessX for X Window

Here I describe AccessX, an option built into X Window version R6 and above. This helps users who have certain disabilites with respect to their abilities to use the keyboard or a mice. If you have other info to put on this page, please tell me about it: stephen@math.missouri.edu.

For certain versions of X Window you may find a built in program called accessx that allows you switch these options on and off. This includes IRIX 6.5 for the SGI, possibly something on the Sun, and DECwindows.

For other versions of X, there are now a number of other programs that do the same task:

• XFree86-4.0 has a utility xf86cfg which allows users to set some of the accessx options.
• A command line interface program xkbset written by me.
• A very limited, but rather easy to understand, program cheap-accessx-0.1.tar.gz.
• Apparently Release 6.6 of X Window (Version 11) will include the Sun and DEC/Compaq-donated accessx program. Look for this when your favorite distribution catches up to X11R6.6.

• Sticky Keys: So for example, to get @, press the SHIFT key, release it, and then press the 2. To write XKB, press SHIFT twice, then xkb, then SHIFT again. Works also with CONTROL and ALT. To switch this on/off, press the SHIFT key 5 times.
• Slow Keys: Causes the keys to work only if they are pressed for a certain amount of time (so accidental key presses don't register). To switch this on/off, press the SHIFT key for 8 seconds.
• Mouse Keys: The numerical key pad may be used as well as the mouse to move the cursor. To switch this on/off, press in this order (holding them down until you are done with the third key): Left SHIFT key, left ALT key, NUM-LOCK key. (Actually Mouse Keys is buggy with respect to acceleration: see bugfix-for-mousekeys.)

• When starting X, have the +accessx switched on. For example, if you start X with the command startx, do it like this:
          startx -- +accessx
• If you use X via xdm, then look for a file called Xservers in a directory that might be called /usr/X11R6/lib/X11/xdm, and make sure it has a line like
          :0 local /usr/X11R6/bin/X +accessx
(OK, I have not tested this - maybe someone else would test it and tell me if it works.)
• Use my utility xkbset as follows:
          xkbset a
• If you are using XFree86 version 4.0.2 or greater: as root edit /usr/X11R6/lib/X11/xkb/X0-config.keyboard (or wherever this file is), and make sure that AccessxKeys appears in a line like
          Controls += RepeatKeys + MouseKeys + MouseKeysAccel + AccessxKeys
  (this file can be created by xf86cfg, or you can just create it yourself).

Natural Math

Polyomino Puzzles

The screensaver xlockmore contains the mode polyominoes, which solves various polyomino puzzles in real time. Use version 5.01 or above (but version 5.00 has a smaller problem set called pentominoes). It may be obtained from here. This has now also been incorporated into the xscreensaver program.

The Spherical Package

The "Fast Exact Closure" Package