(load "snapl.scm")

;; the koch snowflake starts from a triangle
(define koch-start triangle)

;; the koch snowflake editing rule has 4 lines each of which 
;; are 1/3 long
(define koch-program
  '((mark edge (/ 1 3))
    (turn (- angle60))
    (mark edge (/ 1 3))
    (turn (* 2 angle60))
    (mark edge (/ 1 3))
    (turn (- angle60))
    (mark edge (/ 1 3))))

;; this version uses cosine explicitly, and relates
;; more closely to the next part 
(define koch-program
  '((mark edge (/ 1 3))
    (turn (- angle60))
    (mark edge (/ (/ 1 6) (cos angle60)))
    (turn (* 2 angle60))
    (mark edge (/ (/ 1 6) (cos angle60)))
    (turn (- angle60))
    (mark edge (/ 1 3))))

(define snowflake
  (snapl-edit koch-program
    (snapl-edit koch-program
       (snapl-run koch-start))))
(snapl-show snowflake)

;; this version uses a switch to only put in some of the triangles
;; using two line labels: a and b
(define triangle2
  '((turn (- angle60))
    (mark b 1)
    (turn (* 2 angle60))
    (mark b 1)
    (turn (* 2 angle60))
    (mark b 1)))

(define koch-program2
  '((switch (a
             (mark a 1))
            (b
             (mark a (/ 1 3))
             (turn (- angle60))
             (mark b (/ 1 3))
             (turn (* 2 angle60))
             (mark b (/ 1 3))
             (turn (- angle60))
             (mark a (/ 1 3))))))

(define snowflake2
  (snapl-edit koch-program2
    (snapl-edit koch-program2
       (snapl-edit koch-program2
          (snapl-edit koch-program2
              (snapl-run triangle2))))))
(snapl-show snowflake2)

;; this is a square
(define other-start
  '((mark edge 1)
    (turn (/ pi 2))
    (mark edge 1)
    (turn (/ pi 2))
    (mark edge 1)
    (turn (/ pi 2))
    (mark edge 1)))

;; this value needed fine-tuning to get things to look right...
(define almost90 (/ pi 2.07))

;; this is the rule for the second fractal design (note that
;; all the angles are negatived from what was in the above)
(define other-program
  '((mark edge 0.475)
    (turn almost90)
    (mark edge (/ 0.025 (cos almost90)))
    (turn (* -2 almost90))
    (mark edge (/ 0.025 (cos almost90)))
    (turn almost90)
    (mark edge 0.475)))

(define otherflake
  (snapl-edit other-program
    (snapl-edit other-program
    (snapl-edit other-program
       (snapl-run other-start)))))
;(snapl-show otherflake)