# recursive (Sierpinski) triangles
# updated by cmc, 3/3/2015

import turtle
import sys

# start listing_09_04.py from Miller/Ranum:
def drawTriangle(t,p1,p2,p3):
    t.up()
    t.goto(p1)
    t.down()
    t.goto(p2)
    t.goto(p3)
    t.goto(p1)

def midPoint(p1,p2):
    return ((p1[0]+p2[0])/2.0,(p1[1]+p2[1])/2.0)

def sierpinski(myTurtle,p1,p2,p3,depth):
    if depth > 0:
        sierpinski(myTurtle,p1,midPoint(p1,p2),midPoint(p1,p3),depth-1,)
        sierpinski(myTurtle,p2,midPoint(p2,p3),midPoint(p2,p1),depth-1,)
        sierpinski(myTurtle,p3,midPoint(p3,p1),midPoint(p3,p2),depth-1,)
    else:
        drawTriangle(myTurtle,p1,p2,p3)
# end listing_09_04.py

def main():
    '''
      starts the application, and processes first command
      line argument if present - depth of recursion assumed
    '''
    p1 = [-200, -200]
    p2 = [200, -200]
    p3 = [0, 200]
    defaultDepth = 3

    if len(sys.argv) < 2:
        depth = defaultDepth
    else:
        try:
            depth = int(sys.argv[1])
        except:
            print("\nError:", sys.exc_info()[0])
            print("Setting depth to ", defaultDepth)
            depth = defaultDepth

    t = turtle.Turtle()
    t.hideturtle()
    sierpinski(t, p1, p2, p3, depth)
    t.getscreen().exitonclick()

main()