;; Impromptu turtle graphics examples
;; Load and evaluate the turtle-graphics.scm library first
;; Read the comments in that library file for details of the syntax of this implementation
;; 
;; These examples are largely based on those in 
;; David Thornburg's "Discovering Apple Logo" 1983.
;;
;; Note that the colon prior to variable names is a convention from Logo

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; simple commands, evaluate each line/function in turn
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(tg:forward 100)
(tg:right 90)
(tg:forward 50)
(tg:home)
(tg:clear-screen)
(tg:back 40)
(tg:pen-up)
(tg:forward 90)
(tg:pen-down)
(tg:forward 50)
(tg:clean)
(tg:forward 30)
(tg:clear-screen)

;;;;;;;;;;;;;;;;
;; functions
;;;;;;;;;;;;;;;;
(tg:repeat 4 (tg:forward 80) (tg:right 90))
(tg:clear-screen)

(tg:to (square :size)
    (tg:repeat 4 (tg:forward :size) (tg:right 90)))

(square 80)
(square 120)

(tg:clear-screen)
(tg:repeat 6 (square 100) (tg:right 60))

(tg:clear-screen)
(tg:to (poly :size :sides)
    (tg:repeat :sides (tg:forward :size) (tg:right (/ 360 :sides))))

(poly 50 3)
(poly 50 4)
(poly 50 5)
(poly 50 9)

(tg:clear-screen)
(tg:repeat 9 (tg:repeat 7 (tg:forward 200) (tg:right 114)))

(tg:clear-screen)
(tg:repeat 5 (tg:forward 100) (tg:repeat 5 (poly 40 3) (tg:right 72)) (tg:right 72))

(tg:clear-screen)
(tg:to (star)
    (tg:repeat 5 (tg:forward 20) (tg:right 144)))

(star)

(tg:clear-screen)
(tg:to (stars)
    (tg:repeat 8 (tg:set-pc (random) (random) (random) 1) (star) (tg:pen-up) (tg:set-x 30) (tg:pen-down)))

(stars)

(tg:clear-screen)
(tg:to (more-stars)
    (tg:repeat 8 (stars) (tg:pen-up) (tg:set-y 30) (tg:set-x -240) (tg:pen-down)))

(more-stars)

(tg:clear-screen)
(tg:pen-down)
(tg:set-pc 1 0 0 1) ; red

(tg:to (squiral :angle)
    (tg:make :side 0)
    (tg:repeat 100 (tg:forward :side) (tg:right :angle) (set! :side (+ :side 2))))

(squiral 90)

(tg:clear-screen)
(squiral 70)

(tg:clear-screen)
(squiral 118)

(tg:clear-screen)
(squiral 144)

(tg:set-bg 0.3 0.3 0.3 1) ; gray
(tg:clear-screen)
(tg:set-pc 0 1 0.3 1) ; green
(tg:to (closed-spiral size angle increment)
    (tg:repeat 720 (tg:forward size) (tg:right angle) (set! angle (+ angle increment))))

(closed-spiral 7 0 1)

(tg:clear-screen)
(closed-spiral 7 0 7)

(tg:clear-screen)
(closed-spiral 15 1 8)

;;;;;;;;;;;;;;;;;;;;
;; recursion
;;;;;;;;;;;;;;;;;;;;
(tg:set-bg 0 0 0 1) ; black
(tg:clear-screen)
(tg:set-pc 0 0 1 1) ; blue

(tg:to (quad-fractal :size :limit)
    (if (< :size :limit) (tg:forward :size)
        (begin (quad-fractal (/ :size 3) :limit)
               (tg:left 90)
               (quad-fractal (/ :size 3) :limit)
               (tg:right 90)
               (quad-fractal (/ :size 3) :limit)
               (tg:right 90)
               (quad-fractal (/ :size 3) :limit)
               (tg:left 90)
               (quad-fractal (/ :size 3) :limit))))

(tg:clear-screen)
(tg:right 90)
(quad-fractal 243 243)

(tg:clear-screen)
(tg:right 90)
(quad-fractal 243 81)

(tg:clear-screen)
(tg:right 90)
(quad-fractal 243 27)

(tg:clear-screen)
(tg:right 90)
(quad-fractal 243 3)


(tg:set-bg 1 1 1 1) ; white
(tg:clear-screen)
(tg:set-pc 0 1 0 1) ; green

(tg:to (f-tree :size :counter)
    (if (=  :counter 0) 'done
        (begin (tg:left 30)
               (tg:forward (* :size 2))
               (f-tree :size (- :counter 1))
               (tg:back (* :size 2))
               (tg:right 60)
               (tg:forward :size)
               (f-tree :size (- :counter 1))
               (tg:back :size)
               (tg:left 30))))

(tg:clear-screen)
(f-tree 30 5)
(tg:back 100)

;;;;;;;;;;;;;;;;;;;;;;;;
;; psudo 3D
;;;;;;;;;;;;;;;;;;;;;;;;
(tg:set-bg 0.9 0.9 0.9 1) ; light gray
(tg:clear-screen)
(tg:set-pc 0 0 0 1) ; black

(tg:to (escher-box :size :slist)
    (tg:left 60)
    (tg:pen-down)
    (tg:repeat 3 (shade :size (tg:first :slist))
            (set! :slist (tg:but-first :slist))
            (tg:right 120))
    (tg:right 60)
    (hexagon :size))

(tg:to (hexagon :size)
    (tg:pen-up)
    (tg:left 60)
    (tg:forward :size)
    (tg:pen-down)
    (tg:right 120)
    (tg:repeat 6 (tg:forward :size) (tg:right 60))
    (tg:left 120)
    (tg:pen-up)
    (tg:back :size)
    (tg:right 60)
    (tg:pen-down))

(tg:to (shade :size :stripes)
    (tg:make dist (/ :size :stripes))
    (tg:repeat :stripes (tg:forward dist)
            (tg:right 120)
            (tg:forward :size)
            (tg:back :size)
            (tg:left 120))
    (tg:back :size))

(tg:clear-screen)
(escher-box 100 (list 3 5 12))