;; Draws a pyramid with turtle graphics in Scheme
;; The function is "pyramid", the two parameters are "steps" and "len"
;; Use Language PLT/Pretty Big and teachpack turtles.ss

(define (pyramid steps len)
  (begin
    (do ([i 0 (+ i 1)])
      [(>= i steps)]
      (turn 90)
      (draw len)
      (turn -90)
      (draw len))
    (do ([i 0 (+ i 1)])
      [(>= i steps)]
      (draw len)
      (turn -90)
      (draw len)
      (turn 90)))
  (turn 180)
  (draw (* len steps 2))
  (turn 180))

;; command to open the turtles window

(turtles)
;; Draws a pyramid with turtle graphics in Scheme
;; The function is "pyramid", the two parameters are "steps" and "len"
;; Use Language PLT/Pretty Big and teachpack turtles.ss

(define (pyramid steps len)
  (begin
    (do ([i 0 (+ i 1)])
      [(>= i steps)]
      (turn 90)
      (draw len)
      (turn -90)
      (draw len))
    (do ([i 0 (+ i 1)])
      [(>= i steps)]
      (draw len)
      (turn -90)
      (draw len)
      (turn 90)))
  (turn 180)
  (draw (* len steps 2))
  (turn 180))

;; command to open the turtles window

(define (drawSquare side)
    (do ([i 0 (+ i 1)])
    [(>= i 4)]
    (draw side)
    (turn 90)))

(define (rowOfSquares n s)
    (do ([i 0 (+ i 1)])
    [(>= i n)]
    (drawSquare s)
    (move (* s 2))))

(define (pyramid1 n s)
    (do ([i 0 (+ i 1)])
    [(>= i n)]
    (rowOfSquares i s)
    (turn 180)
    (move (* 2 s i))
    (turn 90)
    (move (* 2 s))
    (turn 90)
      ))

(define (pyramid2 n s)
    (do ([i 0 (+ i 1)])
    [(>= i n)]
    (rowOfSquares (+ (* 2 i) 1) s)
    (turn 180)
    (move (+ (* 2 s (+ (* 2 i) 1)) s s))
    (turn 90)
    (move (* 2 s))
    (turn 90)
      ))

(define (checkerboard n s)
    (do ([i 0 (+ i 1)])
    [(>= i n)]
      (rowOfSquares n s)
      (turn 180)
      (move (* n s 2))
      (turn 90)
      (move (* 2 s))
      (turn 90)
      ))

(turtles)