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;; Example 3.27
(define (fib n)
(cond ((= n 0) 0)
((= n 1) 1)
(else (+ (fib (- n 1))
(fib (- n 2))))))
(define memo-fib
(memoize (lambda (n)
(cond ((= n 0) 0)
((= n 1) 1)
(else (+ (memo-fib (- n 1))
(memo-fib (- n 2))))))))
(define (memoize f)
(let ((table (make-table)))
(lambda (x)
(let ((previously-computed-result (lookup x table)))
(or previously-computed-result
(let ((result (f x)))
(insert! x result table)
result))))))
(memo-fib 25)
(fib 25)
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