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Ingy döt Net 2013-10-27 22:24:23 +00:00
parent 6f050a029e
commit 776bba907c
3887 changed files with 59894 additions and 7280 deletions
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Task/Polymorphism/Racket/polymorphism.rkt Normal file
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#lang racket
(define point%
(class* object% (writable<%>) (super-new) (init-field [x 0] [y 0])
(define/public (copy) (new point% [x x] [y y]))
(define/public (show) (format "<point% ~a ~a>" x y))
(define/public (custom-write out) (write (show) out))
(define/public (custom-display out) (display (show) out))))
(define circle%
(class point% (super-new) (inherit-field x y) (init-field [r 0])
(define/override (copy) (new circle% [x x] [y y] [r r]))
(define/override (show) (format "<circle% ~a ~a>" (super show) r))
(define/override (custom-write out) (write (show) out))
(define/override (custom-display out) (display (show) out))))