Deutsch English Français Italiano |
<vc5nmc$1vnei$1@dont-email.me> View for Bookmarking (what is this?) Look up another Usenet article |
Path: ...!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: "B. Pym" <Nobody447095@here-nor-there.org> Newsgroups: comp.lang.lisp,comp.lang.scheme Subject: Re: palindromic number Date: Sun, 15 Sep 2024 04:26:58 -0000 (UTC) Organization: A noiseless patient Spider Lines: 54 Message-ID: <vc5nmc$1vnei$1@dont-email.me> References: <vc55k8$1nud1$1@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Injection-Date: Sun, 15 Sep 2024 06:26:58 +0200 (CEST) Injection-Info: dont-email.me; posting-host="0f1f4abe2f0188b39c05744f5a8843bd"; logging-data="2088402"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+xvclKHQ3leQPrTtgbxUzQ" User-Agent: XanaNews/1.18.1.6 Cancel-Lock: sha1:KDGQ9rQWboV1Dqfk1uLopa9qZcw= Bytes: 2305 B. Pym wrote: > > "A palindromic number reads the same both ways. The largest > > palindrome made from the product of two 2-digit numbers is 9009 > > = 91 x 99. Find the largest palindrome made from the product of > > two 3-digit numbers." > > > Gauche Scheme > > (use srfi-13) ;; string-reverse > > (define (divisor? n m) (= 0 (mod m n))) > > "We don't need no stinkin' loops!" > > (define (prod-of-3-dig-nums? n) > (let1 sq (exact-integer-sqrt n) > (any (is divisor? n) (lrange sq 999)))) > > (define (good? n) > (let1 s (number->string n) > (and (equal? s (string-reverse s)) > (prod-of-3-dig-nums? n)))) > > (find good? (lrange 998001 0 -1)) > ===> > 906609 > > Given: > > (define-syntax is > (syntax-rules () > [(is x) > (lambda (y) (equal? y x))] > [(is compare x) > (lambda (y) (compare y x))] > [(is key compare x) > (lambda (y) (compare (key y) x))])) > "Each new term in the Fibonacci sequence is generated by adding > the previous two terms. By starting with 1 and 2, the first 10 > terms will be: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ... By > considering the terms in the Fibonacci sequence whose values do > not exceed four million, find the sum of the even-valued terms." (do ((a 1 b) (b 2 (+ a b)) (s 0 (if (even? a) (+ a s) s))) ((> a 4000000) s)) ===> 4613732