Examples from CFDG

Context Free Design Grammar (CFDG) is a micro-language designed by Chris Coyne to define 2-dimensional shape grammars (basically L-systems). CFDG is particularly well suited to create repetitive forms with recursion. For a complex example of the language in action, see Chris’ tree example.

Chris released his command-line version as Open Source, and inspired Mark Lentczner and John Horigan to write Context Free, a GUI version that runs on Windows and Mac OS X. Context Free is Open Source, and both the application and source (C++) can be downloaded here. There is no proper manual as such, but the included demos should get you started. Context Free is very fast and allows rendering of the final image to very high-resolution PNG files. Context Free uses the Open Source C++ Anti-Grain Geometry rendering library for 2D graphics

See Wikipedia for an excellent introduction to the subject of context-free grammars: Wikipedia: Context-free grammars.

Also posted on Dataisnature, Boing Boing and Lightcycle.