24 lines
No EOL
513 B
Scheme
24 lines
No EOL
513 B
Scheme
#lang sicp
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; recursive process
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(define (f1 n)
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(if (< n 3)
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n
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(+ (f1 (- n 1))
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(* 2 (f1 (- n 2)))
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(* 3 (f1 (- n 3))))))
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; iterative process
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; loop for n >= 3
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(define (f-iter iter-count acc1 acc2 acc3)
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(let ((new-val (+ acc1 (* 2 acc2) (* 3 acc3))))
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(if (= iter-count 0)
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new-val
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(f-iter (- iter-count 1) new-val acc1 acc2))))
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(define (f2 n)
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(if (< n 3)
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n
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(f-iter (- n 3) (f2 2) (f2 1) (f2 0))))
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; these are just 2,1,0 respectively, but I felt this looks cleaner |