Notes: Friday 8 March 2002
| Schedule |
- Spring Break Reading: finish Part I of GEB
- 18 March: GEB Questions
- Friday, 25 March: Problem Set 6
(define (make-number n)
(lambda (message)
(cond
((eq? message 'value) (lambda (self) n))
((eq? message 'add) (lambda (self other)
(+ (ask self 'value) (ask other 'value))))))))
(define (ask object message . args) (apply (object message) object args))
Inheritance is using the definition of one class to make another class.
(define (make-fraction numer denom)
(let ((super (make-number #f)))
(lambda (message)
(cond
((eq? message 'value) (lambda (self) (/ numer denom)))
((eq? message 'get-denominator) (lambda (self) denom))
((eq? message 'get-numerator) (lambda (self) numer))
(else (super message))))))
The class fraction inherits from number.fraction is a subclass of number.
The superclass of fraction is number.
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Hofstadter's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law. Byrd's Law: It always takes longer than you expect, even when you take into account Hofstadter's Law.
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