# NOTE FOR CANOPY USERS: 'turtle' is based on a GUI called 'tkinter' which is different from 
# what Canopy is based on that's called 'pylab'. Hence, in order to be able to use turtle in
# Canopy, you should do the following:
# Click on Canopy - Preferences - Python, then uncheck 'Use Pylab'.

from turtle import * 
import time

def initturtle():
        
        pencolor('blue')
        
        speed('slowest')
        
        tracer(1)
        
        goto(0,0)
        
        pendown()


def graphword(str):

        for char in str:

            if char == 'F':
                
                forward(100)


            if char == '-':
                
                left(90)


            if char == '[':  # when you see a '[', save the current 'state' of the turtle
                
                (xpos, ypos) = position()  # get current turtle position
               
                angle = heading()  # get current turtle heading angle
               
                TurtleState = (xpos, ypos, angle)  # form a tuple containing the state of the turtle
               
                stack.append(TurtleState)  # store turtle state in a stack


            if char == ']':  # when you see a ']', restore last stored turtle state
                
                stackpointer = len(stack) - 1
                
                (xpos, ypos, angle) = stack[stackpointer]  # retrieve turtle state from stack
                
                del stack[stackpointer]  # once retrieved, delete from stack
                
                goto(xpos, ypos)  # use retrieved info to set the coordinates of the turtle
                
                setheading(angle) # also set heading angle


initturtle()          

stack = list()

graphword('F[-F]F')

done()