# Sample L-System file for drawing a 3D extended Hilbert curve.
#
# Created by Rob Lindeman
# 2005-11-16
#
# The structure of the file is:
# 1. Some number of comment lines, each beginning with a '#' in the first position.
# 2. A line beginning with the word "len" followed by a colon, a space, and then a
#    single integer representing the length of each segment to draw.
# 3. A line beginning with the word "iter" followed by a colon, a space, and then a
#    single integer representing the number of iterations to apply.
# 4. A line beginning with the word "rot" followed by a colon, a space, and then three
#    floating-point numbers, separated by spaces, representing the X, Y, and Z rotations,
#    respectively.
# 5. Zero or more lines beginning with the word "rep" followed by a colon, a space, and then
#    a pair of characters "X,Y". These are used to go through the string that results after
#    applying the production rules "iter" times. For each occurence of "X" in this string,
#    it is replaced with the character "Y". "Y" may be ommitted, in which case all
#    occurences of "X" are removed from the string.
# 6. A line beginning with the word "start" followed by a colon, a space, and then
#    the initial turtle string.
# 7. Some number of production rules of the form: "L: R", where "L" is a single
#    character representing the left-hand side of the rule, and "R" is a sequence
#    of characters representing the replacement string for "L".
len: 1
iter: 2
rot: 90.0 90.0 90.0
rep: A,
rep: B,
rep: C,
rep: D,
start: A
A: B-F+CFC+F-D&F^D-F+&&CFC+F+B//
B: A&F^CFB^F^D^^-F-D^|F^B|FC^F^A//
C: |D^|F^B-F+C^F^A&&FA&F^C+F+B^F^D//
D: |CFB-F+B|FA&F^A&&FB-F+B|FC//