CSC151 2010S, Class 19: Turtle Graphics

Overview:
* Turtle graphics: An example
* Lab.

Admin:
* Things I like to hear: "Sam, you're the best
  professor ever."
* Reading for Friday: Iteration.
* It's Pop Tarts day in CSC 151.
* EC for today's panel on Open Information Culture (4:15 pm Burling).
* EC for Wednesday's gates lecture or Thursday's convo.
* EC for Thursday's CS Extra: Tony Pan on his internship at Microsoft (4:15 3821).
* EC for Friday's CS Table: No Silver Bullet (noon, JRC PDR).
* Advance warning: Polio movie next Thursday, raffle tickets to support Haiti
* EC for Singers concert on Saturday
* Assignment 4 is due.  
* Assignment 5 will be distributed on Friday.

Making Spirals

(define world (image-show (image-new 500 500)))
(define tommy (turtle-new world))

(define angle 15)

(turtle-teleport! tommy 250 250)
(turtle-forward! tommy 5)
(turtle-turn! tommy angle)
(turtle-forward! tommy 6)
(turtle-turn! tommy angle)
(turtle-forward! tommy 7)
(turtle-turn! tommy angle)
(turtle-forward! tommy 8)
(turtle-turn! tommy angle)
(turtle-forward! tommy 9)
(turtle-turn! tommy angle)
(turtle-forward! tommy 10)
(turtle-turn! tommy angle)
(turtle-forward! tommy 11)
(turtle-turn! tommy angle)
(turtle-forward! tommy 12)
(turtle-turn! tommy angle)
(turtle-forward! tommy 13)
(turtle-turn! tommy angle)
(turtle-forward! tommy 14)
(turtle-turn! tommy angle)
(turtle-forward! tommy 15)
(turtle-turn! tommy angle)
(turtle-forward! tommy 16)

-- Simpler

(map (lambda (amt) (turtle-forward! tommy amt)
         (turtle-turn! tommy angle))
     (iota 100))