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2.52.scm
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2.52.scm
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(define (make-vect x y)
(cons x y))
(define (xcor-vect v)
(car v))
(define (ycor-vect v)
(cdr v))
; 2.48
(define (make-segment start end)
(cons start end))
(define (start-segment segment)
(car segment))
(define (end-segment segment)
(cdr segment))
(define (make-frame origin edge1 edge2)
(list origin edge1 edge2))
(define (origin-frame frame)
(car frame))
(define (edge1-frame frame)
(cadr frame))
(define (edge2-frame frame)
(caddr frame))
(define (add-vect v1 v2)
(make-vect
(+ (xcor-vect v1) (xcor-vect v2))
(+ (ycor-vect v1) (ycor-vect v2))))
(define (scale-vect a v)
(make-vect
(* a (xcor-vect v))
(* a (ycor-vect v))))
(define (neg-vect v)
(scale-vect -1 v))
(define (sub-vect v1 v2)
(add-vect v1 (neg-vect v2)))
(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))))))
; Generates JavaScript code for drawing on a canvas
(define (draw-line v1 v2)
(newline)
(display "ctx.beginPath();")
(display (string-append "ctx.moveTo(" (number->string (xcor-vect v1)) "," (number->string (ycor-vect v1)) ");"))
(display (string-append "ctx.lineTo(" (number->string (xcor-vect v2)) "," (number->string (ycor-vect v2)) ");"))
(display "ctx.stroke();"))
;<html>
;<body>
;<canvas width="500" height="500"></canvas>
;<script>
;var canvas = document.querySelector('canvas');
;var ctx = canvas.getContext('2d');
;//TODO: Insert the generated code here
;</script>
;</body>
;</html>
(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)))
(define (transform-painter painter origin corner1 corner2)
(lambda (frame)
(let ((m (frame-coord-map frame)))
(let ((new-origin (m origin)))
(painter
(make-frame new-origin
(sub-vect (m corner1) new-origin)
(sub-vect (m corner2) new-origin)))))))
(define (beside painter1 painter2)
(let ((split-point (make-vect 0.5 0.0)))
(let ((paint-left
(transform-painter painter1
(make-vect 0.0 0.0)
split-point
(make-vect 0.0 1.0)))
(paint-right
(transform-painter painter2
split-point
(make-vect 1.0 0.0)
(make-vect 0.5 1.0))))
(lambda (frame)
(paint-left frame)
(paint-right frame)))))
(define (flip-horiz painter)
(transform-painter painter
(make-vect 1.0 0.0)
(make-vect 0.0 0.0)
(make-vect 1.0 1.0)))
(define (flip-vert painter)
(transform-painter painter
(make-vect 0.0 1.0)
(make-vect 1.0 1.0)
(make-vect 0.0 0.0)))
(define (rotate-90 painter)
(transform-painter painter
(make-vect 1.0 0.0)
(make-vect 1.0 1.0)
(make-vect 0.0 0.0)))
(define (rotate-90-clockwise painter)
(transform-painter painter
(make-vect 0.0 1.0)
(make-vect 0.0 0.0)
(make-vect 1.0 1.0)))
(define (rotate-180 painter)
(transform-painter painter
(make-vect 1.0 1.0)
(make-vect 0.0 1.0)
(make-vect 1.0 0.0)))
(define (below painter1 painter2)
(rotate-90 (beside (rotate-90-clockwise painter1) (rotate-90-clockwise painter2))))
(define (right-split painter n)
(if (= n 0)
painter
(let ((smaller (right-split painter (- n 1))))
(beside painter (below smaller smaller)))))
(define (up-split painter n)
(if (= n 0)
painter
(let ((smaller (up-split painter (- n 1))))
(below painter (beside smaller smaller)))))
(define (corner-split painter n)
(if (= n 0)
painter
(let ((up (up-split painter (- n 1)))
(right (right-split painter (- n 1))))
(let ((top-left (beside up up))
(bottom-right (below right right))
(corner (corner-split painter (- n 1))))
(beside (below painter top-left)
(below bottom-right corner))))))
(define (square-limit painter n)
(let ((quarter (corner-split painter n)))
(let ((half (beside (flip-horiz quarter) quarter)))
(below (flip-vert half) half))))
(define base-frame
(make-frame
(make-vect 0 0)
(make-vect 500 0)
(make-vect 0 500)))
; Simplified version of the wave pattern
(define (wave frame)
((segments->painter
(list
(make-segment (make-vect 0 0) (make-vect 0.5 0.5))
(make-segment (make-vect 0 1) (make-vect 0.5 0.5))
(make-segment (make-vect 0.5 1) (make-vect 0.5 0.5))
(make-segment (make-vect 1 0.5) (make-vect 0.5 0.5))
(make-segment (make-vect 1 0) (make-vect 0.5 0.5)))) frame))
(newline)
(newline)
(display "square-limit:")
((square-limit wave 5) base-frame)
; 2.52 a. Even more simplified version of the wave pattern
(define (wave frame)
((segments->painter
(list
(make-segment (make-vect 0 0) (make-vect 0.5 0.5))
(make-segment (make-vect 0.5 0.5) (make-vect 1 0.5)))) frame))
; 2.52 b. Change pattern produced by corner-split
(define (corner-split painter n)
(if (= n 0)
painter
(let ((up (up-split painter (- n 1)))
(right (right-split painter (- n 1))))
(let ((corner (corner-split painter (- n 1))))
(beside (below painter up)
(below right corner))))))
; 2.52 c. Modify square-limit
(define (square-of-four tl tr bl br)
(lambda (painter)
(let ((top (beside (tl painter) (tr painter)))
(bottom (beside (bl painter) (br painter))))
(below bottom top))))
(define (identity x) x)
(define (square-limit painter n)
(let ((combine4 (square-of-four identity flip-horiz
flip-vert rotate-180)))
(combine4 (corner-split painter n))))