;;;
;;; lsystem.ss
;;; UVA CS200 Spring 2002
;;; Problem Set 3
;;;

(load "curve.ss")

;;;
;;; Abstraction for representing L-System Commands using lists.
;;;

;;; CommandSequence ::= (CommandList)
(define make-lsystem-command list)

;;;
;;; We represent the different commands as lists where the first item in the
;;; list is a tag that indicates the type of command: 'f for forward, 'r for rotate
;;; and 'o for offshoot.  We use quoted letters --- 'f is short for
;;; (quote f) --- to make tags - they evaluate to the letter after the quote.
;;;

;;; Command ::= F <Distance>
(define (make-forward-command distance) (cons 'f distance))

;;; Command ::= R <Angle>
(define (make-rotate-command angle) (cons 'r angle))

;;; Command ::= O <CommandSequence>
(define (make-offshoot-command commandsequence) (cons 'o commandsequence))

(define (is-lsystem-command? lcommand)
  (or (is-forward? lcommand)
      (is-rotate? lcommand)
      (is-offshoot? lcommand)))

;;;
;;; Flattening Command Lists
;;;

(define (flatten-commands ll)
  (if (null? ll) 
      ll
      (if (is-lsystem-command? (car ll))
	  (cons (car ll) (flatten-commands (cdr ll)))
	  (flat-append (car ll) (flatten-commands (cdr ll))))))

(define (flat-append lst ll)
  (if (null? lst) ll
      (cons (car lst) (flat-append (cdr lst) ll))))

;;;
;;; Question 5:
;;;

(define (rewrite-lcommands lcommands replacement)
  (flatten-commands
   (map 
   ; Procedure to apply to each command
   lcommands)))

;;;
;;; Question 6:
;;;


(define (make-lsystem-fractal replace-commands start level)
  #f ;;; Fill this in 
  )

;;; 
;;; L-System commands for the tree fractal
;;;
;;; F1 ::= (F1 O(R30 F1) F1 O(R-60 F1) F1) 

(define tree-commands
  (make-lsystem-command 
   (make-forward-command 1)
   (make-offshoot-command
    (make-lsystem-command
     (make-rotate-command 30) 
     (make-forward-command 1)))
   (make-forward-command 1)
   (make-offshoot-command
    (make-lsystem-command
     (make-rotate-command -60) 
     (make-forward-command 1)))
   (make-forward-command 1)))

(define (make-tree-fractal level)
  (make-lsystem-fractal tree-commands (make-lsystem-command (make-forward-command 1)) level))

(define (draw-lsystem-fractal lcommands)
  (draw-curve-points (position-curve (convert-to-curve lcommands) 0.5 0.1) 50000))

;;;
;;; Set up a graphics window
;;;

(close-graphics)
(open-graphics)

;;; This window is hard coded into the drawing routines, so we don't need to remember
;;; to pass it.

(define window (make-window window-width window-height "CS 200 Fractals"))