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55 lines
1.4 KiB
Scheme
55 lines
1.4 KiB
Scheme
;; Temporary test file, try with the ack function
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(import (scheme base)
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(srfi 69)
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(scheme write))
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(define (memoize function)
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(let ((table (make-hash-table))) ;(make-equal?-map)))
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(lambda args
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(apply values
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;(map-get table
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(hash-table-ref table
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args
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;; If the entry isn't there, call the function.
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(lambda ()
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(call-with-values
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(lambda () (apply function args))
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(lambda results
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;(map-put! table args results)
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(hash-table-set! table args results)
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results))))))))
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(define (fnc x y) (+ x y))
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(define mfnc (memoize fnc))
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(write (mfnc 1 1)) (newline)
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(write (mfnc 1 1)) (newline)
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; Original versions:
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(define (ack m n)
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(cond ((= m 0) (+ n 1))
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((= n 0) (ack (- m 1) 1))
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(else (ack (- m 1) (ack m (- n 1))))))
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(define (fib n)
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(if (< n 2)
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n
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(+ (fib (- n 1))
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(fib (- n 2)))))
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; Fast versions:
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;(define ack (memoize _ack))
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;(define (_ack m n)
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; (cond ((= m 0) (+ n 1))
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; ((= n 0) (ack (- m 1) 1))
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; (else (ack (- m 1) (ack m (- n 1))))))
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;
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;(define fib (memoize _fib))
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;(define (_fib n)
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; (if (< n 2)
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; n
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; (+ (fib (- n 1))
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; (fib (- n 2)))))
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(write (ack 3 12))
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(newline)
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(write (fib 40))
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