37 lines
1.3 KiB
Racket
37 lines
1.3 KiB
Racket
;; The first three lines of this file were inserted by DrRacket. They record metadata
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;; about the language level of this file in a form that our tools can easily process.
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#reader(lib "htdp-beginner-reader.ss" "lang")((modname rotating-triangle) (read-case-sensitive #t) (teachpacks ()) (htdp-settings #(#t constructor repeating-decimal #f #t none #f ())))
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(require picturing-programs)
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(define R 60)
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(define SIDE (* R (sqrt 3)))
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(define TRI (triangle SIDE "solid" "blue"))
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(define CIRC (circle R "solid" "white"))
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(define tricirc (overlay/xy TRI
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(- (/ SIDE 2) R) 0
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CIRC))
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(define (rotate-1 pic)
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(rotate 1 pic))
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"Triangle rotating by itself (with its top and left attached to the top and left of the window):"
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(big-bang TRI
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(on-tick rotate-1 .05)
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(check-with image?)
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(on-draw show-it))
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"Triangle rotating around its center:"
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(big-bang tricirc
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(on-tick rotate-1 .05)
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(check-with image?)
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(on-draw show-it))
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;show-on-yellow : image -> image
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(define (show-on-yellow pic)
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(overlay pic (rectangle (* 2 R) (* 2 R) "solid" "yellow")))
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"Triangle rotating around its center, on a yellow background:"
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(big-bang tricirc
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(on-tick rotate-1 .05)
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(check-with image?)
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(on-draw show-on-yellow))
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