lsystem.py

"""
Author: Andrija Radica

Računalno crtanje fraktala
Večer Matematike 6. prosinca, 2018.


Symbol interpretations:

F, G	Go forward by some number of units
f       Go forward by some number of units but don't draw
B	    Go backward by some number of units
-	    Turn right by some degrees
+	    Turn left by some degrees

"""

import turtle


def applyRules(string, rules):
    newstr = ""
    for char in string:
        if char in rules:
            newstr += rules[char]
        else:
            newstr += char
    return newstr


def drawSystem(turtle, instructions, angle, d):
    stack = []
    for cmd in instructions:
        if cmd == "F" or cmd == "G":
            turtle.forward(d)

        elif cmd == "[":
            stack.append((turtle.xcor(), turtle.ycor(), turtle.heading()))

        elif cmd == "]":
            turtle.penup()
            x, y, h = stack.pop()
            turtle.setpos(x, y)
            turtle.setheading(h)
            turtle.pendown()

        elif cmd == "f":
            turtle.penup()
            turtle.forward(d)
            turtle.pendown()

        elif cmd == "B":
            turtle.backward(d)

        elif cmd == "-":
            turtle.right(angle)
            
        elif cmd == "+":
            turtle.left(angle)


#axiom
string = "F"
#rule dictionary
rules = {
    "F": "F[+F]F[-F]F"
}

angle = 25.7
iterations = 5


#number of iterations
for i in range(iterations):
    string = applyRules(string, rules)
    #print(string)

T = turtle.Turtle()
T.speed("fastest")
T._tracer(2, 0)

wn = turtle.Screen()
drawSystem(T, string, angle, 2)
T._update()
wn.exitonclick()