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Ingy döt Net 2015-02-20 09:02:09 -05:00
parent 00a190b0a6
commit 91df62d461
5697 changed files with 93386 additions and 804 deletions
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17
Task/Left-factorials/Racket/left-factorials.rkt Normal file
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#lang racket
(define ! (let ((rv# (make-hash))) (λ (n) (hash-ref! rv# n (λ () (if (= n 0) 1 (* n (! (- n 1)))))))))
(define (!n n)
;; note that in-range n is from 0 to n-1 inclusive
(for/sum ((k (in-range n))) (! k)))
(define (dnl. s) (for-each displayln s))
(dnl
"Display the left factorials for:"
"zero through ten (inclusive)"
(pretty-format (for/list ((i (in-range 0 (add1 10)))) (!n i)))
"20 through 110 (inclusive) by tens"
(pretty-format (for/list ((i (in-range 20 (add1 110) 10))) (!n i)))
"Display the length (in decimal digits) of the left factorials for:"
"1,000, 2,000 through 10,000 (inclusive), by thousands."
(pretty-format (for/list ((i (in-range 1000 10001 1000))) (add1 (order-of-magnitude (!n i))))))