Echon

A simple library to generate L-systems for Nim.

Just call generateSystem(start: string, p: seq[Prule], cycle: int) where start is your intial word, p is a seq of replacement rules like (sym: 'A', word: "Hello World!") and cycle is the number of recursions before the function returns its result.

Be careful:

generateSystem("F--F--F", @[(sym: 'F', word: "F+F--F+F")], cycle)

with a cycle > 15 or so will take a really long time to generate. I'm going to optimize this furher, especially with the lazy evaluation implementaion, but for now you have to accept the somewhat slow implementation. Sorry. :(

For example you get something like this:

  check generateSystem("A", @[(sym: 'A', word: "ABCA")], 0) == "ABCA"
  check generateSystem("A", @[(sym: 'A', word: "AB"), (sym: 'B', word: "CC")], 0) == "AB"
  check generateSystem("C", @[(sym: 'A', word: "AB"), (sym: 'B', word: "CC")], 0) == "C"
  check generateSystem("AA", @[(sym: 'A', word: "AB"), (sym: 'B', word: "CC")], 0) == "ABAB"
  check generateSystem("AA", @[(sym: 'A', word: "AB"), (sym: 'B', word: "CC")], 1) == "ABCCABCC"
  check generateSystem("ABC", @[(sym: 'A', word: "AB"), (sym: 'B', word: "CC")], 1) == "ABCCCCC"
  check generateSystem("A", @[(sym: 'A', word: "Hello World!")], 0) == "Hello World"
  check generateSystem("F--F--F", @[(sym: 'F', word: "F+F--F+F")], 0) == "F+F--F+F--F+F--F+F--F+F--F+F"

The last one describes a version of the Koch curve.

If something is unclear, please let me know.