38 lines
942 B
Plaintext
38 lines
942 B
Plaintext
; simple version
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(define (A m n)
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(cond
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((= m 0) (+ n 1))
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((= n 0) (A (- m 1) 1))
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(else (A (- m 1) (A m (- n 1))))))
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(print "simple version (A 3 6): " (A 3 6))
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; smart (lazy) version
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(define (ints-from n)
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(cons* n (delay (ints-from (+ n 1)))))
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(define (knuth-up-arrow a n b)
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(let loop ((n n) (b b))
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(cond ((= b 0) 1)
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((= n 1) (expt a b))
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(else (loop (- n 1) (loop n (- b 1)))))))
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(define (A+ m n)
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(define (A-stream)
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(cons*
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(ints-from 1) ;; m = 0
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(ints-from 2) ;; m = 1
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;; m = 2
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(lmap (lambda (n)
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(+ (* 2 (+ n 1)) 1))
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(ints-from 0))
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;; m = 3
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(lmap (lambda (n)
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(- (knuth-up-arrow 2 (- m 2) (+ n 3)) 3))
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(ints-from 0))
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;; m = 4...
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(delay (ldrop (A-stream) 3))))
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(llref (llref (A-stream) m) n))
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(print "extended version (A 3 6): " (A+ 3 6))
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