15 lines
670 B
Racket
15 lines
670 B
Racket
#lang racket
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(define point%
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(class* object% (writable<%>) (super-new) (init-field [x 0] [y 0])
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(define/public (copy) (new point% [x x] [y y]))
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(define/public (show) (format "<point% ~a ~a>" x y))
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(define/public (custom-write out) (write (show) out))
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(define/public (custom-display out) (display (show) out))))
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(define circle%
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(class point% (super-new) (inherit-field x y) (init-field [r 0])
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(define/override (copy) (new circle% [x x] [y y] [r r]))
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(define/override (show) (format "<circle% ~a ~a>" (super show) r))
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(define/override (custom-write out) (write (show) out))
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(define/override (custom-display out) (display (show) out))))
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