26 lines
941 B
Racket
26 lines
941 B
Racket
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#lang racket
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(require 2htdp/universe pict racket/draw)
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(define ((polyspiral width height segment-length-increment n-segments) tick/s/28)
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(define turn-angle (degrees->radians (/ tick/s/28 8)))
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(pict->bitmap
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(dc (λ (dc dx dy)
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(define old-brush (send dc get-brush))
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(define old-pen (send dc get-pen))
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(define path (new dc-path%))
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(define x (/ width #i2))
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(define y (/ height #i2))
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(send path move-to x y)
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(for/fold ((x x) (y y) (l segment-length-increment) (a #i0))
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((seg n-segments))
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(define x′ (+ x (* l (cos a))))
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(define y′ (+ y (* l (sin a))))
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(send path line-to x y)
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(values x′ y′ (+ l segment-length-increment) (+ a turn-angle)))
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(send dc draw-path path dx dy)
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(send* dc (set-brush old-brush) (set-pen old-pen)))
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width height)))
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(animate (polyspiral 400 400 2 1000))
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