Fun with Lindenmayer systems

Lindenmayer systems (L-systems) produce fractal pictures using recursion to
rewrite a string of symbols, together with a drawing mechanism to convert
symbols to drawing elements. M4 is a natural choice for recursion,
and dpic macros are suitable for controlling drawing actions.

The number of picture elements can be quite large and can overflow
the capacity of LaTeX, so the capabilities of dpic to produce diagrams
without invoking LaTeX are needed.

Many of these examples are credited to Paul Bourke and
others, see http://paulbourke.net/fractals/lsys/ See also
https://en.wikipedia.org/wiki/L-system

Required software:
m4   present on any unix-like system and available free for others
dpic see https://gitlab.com/aplevich/dpic

Type "make" to produce examples.html which displays the diagrams.
To test an individual diagram, copy the m4 source into test.m4
and type "make tst"

Type "make clean" to clean up.
