python (3.11.7)
1 #!/usr/bin/env python3
2 """ turtle-example-suite:
3
4 xtx_lindenmayer_indian.py
5
6 Each morning women in Tamil Nadu, in southern
7 India, place designs, created by using rice
8 flour and known as kolam on the thresholds of
9 their homes.
10
11 These can be described by Lindenmayer systems,
12 which can easily be implemented with turtle
13 graphics and Python.
14
15 Two examples are shown here:
16 (1) the snake kolam
17 (2) anklets of Krishna
18
19 Taken from Marcia Ascher: Mathematics
20 Elsewhere, An Exploration of Ideas Across
21 Cultures
22
23 """
24 ################################
25 # Mini Lindenmayer tool
26 ###############################
27
28 from turtle import *
29
30 def replace( seq, replacementRules, n ):
31 for i in range(n):
32 newseq = ""
33 for element in seq:
34 newseq = newseq + replacementRules.get(element,element)
35 seq = newseq
36 return seq
37
38 def draw( commands, rules ):
39 for b in commands:
40 try:
41 rules[b]()
42 except TypeError:
43 try:
44 draw(rules[b], rules)
45 except:
46 pass
47
48
49 def main():
50 ################################
51 # Example 1: Snake kolam
52 ################################
53
54
55 def r():
56 right(45)
57
58 def l():
59 left(45)
60
61 def f():
62 forward(7.5)
63
64 snake_rules = {"-":r, "+":l, "f":f, "b":"f+f+f--f--f+f+f"}
65 snake_replacementRules = {"b": "b+f+b--f--b+f+b"}
66 snake_start = "b--f--b--f"
67
68 drawing = replace(snake_start, snake_replacementRules, 3)
69
70 reset()
71 speed(3)
72 tracer(1,0)
73 ht()
74 up()
75 backward(195)
76 down()
77 draw(drawing, snake_rules)
78
79 from time import sleep
80 sleep(3)
81
82 ################################
83 # Example 2: Anklets of Krishna
84 ################################
85
86 def A():
87 color("red")
88 circle(10,90)
89
90 def B():
91 from math import sqrt
92 color("black")
93 l = 5/sqrt(2)
94 forward(l)
95 circle(l, 270)
96 forward(l)
97
98 def F():
99 color("green")
100 forward(10)
101
102 krishna_rules = {"a":A, "b":B, "f":F}
103 krishna_replacementRules = {"a" : "afbfa", "b" : "afbfbfbfa" }
104 krishna_start = "fbfbfbfb"
105
106 reset()
107 speed(0)
108 tracer(3,0)
109 ht()
110 left(45)
111 drawing = replace(krishna_start, krishna_replacementRules, 3)
112 draw(drawing, krishna_rules)
113 tracer(1)
114 return "Done!"
115
116 if __name__=='__main__':
117 msg = main()
118 print(msg)
119 mainloop()
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