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; --- Vectors 2.46 ---
(define (make-vect x y) (list x y))
(define (xcor-vect v) (car v))
(define (ycor-vect v) (cadr v))
(define (add-vect v w) (make-vect
(+ (xcor-vect v) (xcor-vect w))
(+ (ycor-vect v) (ycor-vect w))))
(define (sub-vect v w) (make-vect
(- (xcor-vect v) (xcor-vect w))
(- (ycor-vect v) (ycor-vect w))))
(define (scale-vect s v) (make-vect
(* s (xcor-vect v))
(* s (ycor-vect v))))
(define origin (make-vect 0 0))
(define one-one (make-vect 1 1))
(define xunit (make-vect 1 0))
(define yunit (make-vect 0 1))
(define half-half (make-vect 0.5 0.5))
; -- Frames 2.47 --
; --- frame with list representation ---
(define (make-frame origin edge1 edge2)
(list origin edge1 edge2))
(define (origin-frame f) (car f))
(define (edge1-frame f) (cadr f))
(define (edge2-frame f) (caddr f))
; --- frame with cons representation ---
(define (make-frame-cons origin edge1 edge2)(cons origin (cons edge1 edge2)))
(define (origin-frame-cons f) (car f))
(define (edge1-frame-cons f) (car (cdr f)))
(define (edge2-frame-cons f) (cdr (cdr f)))
; --- frame segment ---
(define (make-segment start end) (list start end))
(define (start-segment s) (car s))
(define (end-segment s) (cadr s))
; -- defined function from SICP text
(define (frame-coord-map frame)
(lambda (v)
(add-vect
(origin-frame frame)
(add-vect (scale-vect (xcor-vect v)
(edge1-frame frame))
(scale-vect (ycor-vect v)
(edge2-frame frame))))))
(define (draw-line p1 p2)
(display "Draw: ")(display p1)(display " -> ")(display p2)(newline))
(define (segments->painter segment-list)
(lambda (frame)
(for-each
(lambda (segment)
(draw-line
((frame-coord-map frame) (start-segment segment))
((frame-coord-map frame) (end-segment segment))))
segment-list)))
; -- 2.49 -- some painters
(define (outline-frame f)
((segments->painter
(list (make-segment origin yunit)
(make-segment yunit one-one)
(make-segment one-one xunit)
(make-segment xunit origin))) f))
(define (draw-X f)
((segments->painter
(list (make-segment origin one-one)
(make-segment xunit yunit))) f))
(define (mid-point A B) (scale-vect .5 (add-vect A B)))
(define (diamond f)
((segments->painter
(list
(make-segment (make-vect .5 0) (make-vect 1 .5))
(make-segment (make-vect 1 .5) (make-vect .5 1))
(make-segment (make-vect .5 1) (make-vect 0 .5))
(make-segment (make-vect 0 .5) (make-vect .5 0)))) f))