The code below memoizes a function.
As an example, fibonacci is memoized.
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(define (fib n) | |
(cond ((= n 0) 0) | |
((= n 1) 1) | |
(else (+ (fib (- n 1)) | |
(fib (- n 2)))))) | |
;; The memoized version of the same procedure is | |
(define memo-fib | |
(memoize (lambda (n) | |
(cond ((= n 0) 0) | |
((= n 1) 1) | |
(else (+ (memo-fib (- n 1)) | |
(memo-fib (- n 2)))))))) | |
;; where the memoizer is defined as | |
(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)))))) |