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Line 346: |
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<lang racket>#lang racket |
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<lang racket>#lang racket |
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(define ! (let ((rv# ( make-hash))) (λ (n) (hash-ref! rv# n ( λ () (if ( = n 0) 1 (* n (! ( - n 1))))))))) |
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(define ! |
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(let ((memo# (make-hash))) |
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( lambda (n) (hash-ref! memo# n ( lambda () (if ( zero? n) 1(* n (! ( sub1 n))))))))) |
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(define (!n n) |
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(define (!n n) |
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(for/sum ((k (in-range n))) (! k))) |
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(for/sum ((k (in-range n))) (! k))) |
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(define !n-digits (compose add1 order-of-magnitude !n)) |
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(define (dnl. s) (for-each displayln s)) |
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(dnl |
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"Display the left factorials for:" |
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(define (dln . s) |
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"zero through ten (inclusive)" |
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(for-each displayln s)) |
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(pretty- format (for/list ((i (in-range 0 (add1 10)))) (!n i))) |
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"20 through 110 (inclusive) by tens" |
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(dln "Display the left factorials for:" |
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(pretty- format (for/list ((i (in-range 20 (add1 110) 10))) (!n i))) |
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"zero through ten (inclusive)" ) |
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"Display the length (in decimal digits) of the left factorials for:" |
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(pretty- print (for/list ((i (in-range 0 (add1 10)))) (!n i))) |
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"1,000, 2,000 through 10,000 (inclusive), by thousands." |
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(pretty- format (for/list ((i (in-range 1000 10001 1000))) (add1 (order-of-magnitude (! n i ))))))</lang> |
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(dln "20 through 110 (inclusive) by tens" ) |
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(pretty- print (for/list ((i (in-range 20 (add1 110) 10))) (!n i))) |
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(dln "Display the length (in decimal digits) of the left factorials for:" |
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"1,000, 2,000 through 10,000 (inclusive), by thousands." ) |
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(pretty- print (for/list (( !i -len (sequence-map !n-digits (in-range 1000 10001 1000 )))) !i -len))</lang> |
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{{out}} |
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{{out}} |
