// output of ./demo/comb/stringsubst-demo.cc:
// Description:
//% String substitution engine (Lindenmayer system, or L-system).

arg 1: 7 == maxn  [Max depth]  default=7
arg 2: "A" == start  [Start symbol(s)]  default="A"
args 3,4,... : [Rules:  sym1 rep1  sym2 rep2  [... symN repN]]
Example: ./bin 7 A  A x  x xA

------------- rabbit sequence: -------------
Number of symbols = 2
Start: 0
Rules:
  0 --> 1
  1 --> 10
-------------
0:   (#=1)
  0
1:   (#=1)
  1
2:   (#=2)
  10
3:   (#=3)
  101
4:   (#=5)
  10110
5:   (#=8)
  10110101
6:   (#=13)
  1011010110110
7:   (#=21)
  101101011011010110101

------------- Thue-Morse sequence: -------------
Number of symbols = 2
Start: 0
Rules:
  0 --> 01
  1 --> 10
-------------
0:   (#=1)
  0
1:   (#=2)
  01
2:   (#=4)
  0110
3:   (#=8)
  01101001
4:   (#=16)
  0110100110010110
5:   (#=32)
  01101001100101101001011001101001
6:   (#=64)
  0110100110010110100101100110100110010110011010010110100110010110

------------- Dragon curve (90deg turns): -------------
Number of symbols = 4
Start: F
Rules:
  F --> F+G+
  G --> -F-G
  + --> +
  - --> -
-------------
0:   (#=1)
  F
1:   (#=4)
  F+G+
2:   (#=10)
  F+G++-F-G+
3:   (#=22)
  F+G++-F-G++-F+G+--F-G+
4:   (#=46)
  F+G++-F-G++-F+G+--F-G++-F+G++-F-G+--F+G+--F-G+
5:   (#=94)
  F+G++-F-G++-F+G+--F-G++-F+G++-F-G+--F+G+--F-G++-F+G++-F-G++-F+G+--F-G+--F+G++-F-G+--F+G+--F-G+