Xah Code

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Math & Programing, tutorials & essays. There are 3.4 thousand articles. Use the search box on top to find what you are looking for. For latest articles, subscribe: ProgramingWeb DevEmacsMath.

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Math reference works and essays. Full index at Xah Math. The following are popular topics.

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Visual Dictionary of Special Plane Curves

A dictionary of plane curves, with history, definition, formulas, and properties. Heavily enhanced with illustrations, video animations, GeoGebra interactive applet, and Mathematica notebooks. (70+ pages)

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Surface Gallery

60+ surfaces in mostly differential geometry and 30+ minimal surfaces. Moebius strip, klein bottle, cross-cap, pseudosphere, hyperboloid, minimal surfaces… (70+ pages)

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Wallpaper Groups

A exposition on wallpaper groups, with illustrations of the 17 wallpaper groups and a wallpaper gallery. Technically, the derivation of all discontinuous groups of rotation and translation in the plane. (7+ pages, 100+ illustrations)

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Math Graphics Gallery

A collection of mathematical images. We all know mathematics is beautiful, but did you know that math can appear beautiful too?

Includes two critical essays: Algorithmic Mathematical Art that surveys and defines the subject, and Geometry: Requirements for a Visualization System for 2020.

Great Math Programs

A annotated listing of 100+ excellent recreational math programs. You'll find polyhedra & Rubic cubes, curves & surfaces, fractals & L-systems, tilings & symmetry, game of hex & game of life, go & five-in-a-row, peg solitare & polyominos, …

Computing & its People

Tutorials, Critiques, Commentaries on aspects of the computing industry, technical & social. Siphon my knowledge into your brain; assimilate my sensibilities to your spine. Over 1k articles. Index at Computing & its People.


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Emacs Lisp



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Perl & Python

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POV-Ray & 3D Geometry Programing


Unicode Gallery & Tutorial ∑ ∞ π © ™ § ☺ ♀ ♂ ♥


Keyboards, Layouts, Hotkeys, Macros, RSI ⌨


on Programing Languages