This is very similar to yesterday's L-System Fractal Generator except this version introduces bracket operators to save and restore state. It also uses : for defining derivation rules rather than -> because it is easier to type.

Samples

• Plant 1
• Plant 2
• Plant 3
• Cactus flower
• Palm Frond
• Tangled Tinsel

Example

w: F
F: F+F

On the first iteration, we look up the rule for w. The output string is F

On the second iteration, we replace every F in the input string with F+F. The output string is F+F

On the third iteration, we replace every F in the input string with F+F. The output string is F+F+F+F

And so on...

After running n iterations, the output string is used as drawing instructions. The pen starts at the origin aiming north.

• Uppercase letter: draw a line one unit in the current direction
• +: rotate a degrees counterclockwise
• -: rotate a degrees clockwise
• Lowercase letter: move one unit in the current direction without drawing a line
• [: save the current location and direction
• ]: restore location and direction
• Any other characters are ignored

Further reading: Chapter 1.6 of The Algorithmic Beauty of Plants