From: Stefan Israelsson Tampe <stefan.itampe@gmail.com>
To: guile-devel@gnu.org, guile-user@gnu.org
Subject: Fun with guile, Erastones + goldbach conjecture
Date: Tue, 09 Apr 2013 00:03:11 +0200 [thread overview]
Message-ID: <1551498.g80VkUsTQo@warperdoze> (raw)
[-- Attachment #1: Type: text/plain, Size: 1806 bytes --]
Hi all,
The program below is an interesting variant of a sieve that given an
even number seams to constructs two primes that added together becomes
the even
number, the file below does this construction for n = 3 ... 1000.
Have fun!
/Stefan
(use-modules (srfi srfi-1))
(define (analyze k)
(define n (* k 2))
(define l (apply circular-list (map (lambda (X) #f) (iota n))))
(define (shift l k)
(let loop ((l l) (k k))
(if (= k 0)
l
(loop (cdr l) (- k 1)))))
(define (next loop)
(let lp ((ll l) (i 0))
(if (= i n)
l
(if (car ll)
(lp (cdr ll) (+ i 1))
(loop i l 0)))))
(define (M)
(let lp ((l l) (k n) (M -1))
(if (= k 0)
M
(let ((c (caar l)))
(if (< M c)
(lp (cdr l) (- k 1) c)
(lp (cdr l) (- k 1) M))))))
(define (place x)
(let loop ((ll l) (i 0))
(if (equal? (car ll) x)
i
(loop (cdr ll) (+ i 1)))))
(set-car! (cdr l) (cons 1 0))
(set-car! (shift l (- n 1)) (cons 1 0))
(let loop ((m 2) (ll l) (k 0))
(let ((ll (shift ll m)))
(if (and (pair? (car ll)) (eq? (caar ll) m))
(next loop)
(begin
(unless (car ll) (set-car! ll (cons m k)) (set! k (+ k 1)))
(loop m ll k)))))
(let* ((M (M))
(ll (let lp ((ll l) (k n))
(if (= k 0)
'()
(cons (car ll) (lp (cdr ll) (- k 1))))))
(ll (fold (lambda (k r)(if (eq? (car k) M) (cons k r) r)) '() ll))
(ll (sort ll (lambda (x y) (< (cdr x) (cdr y))))))
(cond
((= (length ll) 1)
(* (place (car ll)) 2))
(else
(+ (place (car ll)) (place (car (last-pair ll))))))))
(let lp ((i 3))
(if (= i 1000)
(pk 'ok)
(begin
(if (not (= (* 2 i) (analyze i)))
(format #t "~a != (analyze ~a) == ~a~%" (* 2 i) (* 2 i)
(analyze (* 2i))))
(lp (+ i 1)))))
[-- Attachment #2: goldbach.scm --]
[-- Type: text/x-scheme, Size: 1560 bytes --]
(use-modules (srfi srfi-1))
(define (analyze k)
(define n (* k 2))
(define l (apply circular-list (map (lambda (X) #f) (iota n))))
(define (shift l k)
(let loop ((l l) (k k))
(if (= k 0)
l
(loop (cdr l) (- k 1)))))
(define (next loop)
(let lp ((ll l) (i 0))
(if (= i n)
l
(if (car ll)
(lp (cdr ll) (+ i 1))
(loop i l 0)))))
(define (M)
(let lp ((l l) (k n) (M -1))
(if (= k 0)
M
(let ((c (caar l)))
(if (< M c)
(lp (cdr l) (- k 1) c)
(lp (cdr l) (- k 1) M))))))
(define (place x)
(let loop ((ll l) (i 0))
(if (equal? (car ll) x)
i
(loop (cdr ll) (+ i 1)))))
(set-car! (cdr l) (cons 1 0))
(set-car! (shift l (- n 1)) (cons 1 0))
(let loop ((m 2) (ll l) (k 0))
(let ((ll (shift ll m)))
(if (and (pair? (car ll)) (eq? (caar ll) m))
(next loop)
(begin
(unless (car ll) (set-car! ll (cons m k)) (set! k (+ k 1)))
(loop m ll k)))))
(let* ((M (M))
(ll (let lp ((ll l) (k n))
(if (= k 0)
'()
(cons (car ll) (lp (cdr ll) (- k 1))))))
(ll (fold (lambda (k r)(if (eq? (car k) M) (cons k r) r)) '() ll))
(ll (sort ll (lambda (x y) (< (cdr x) (cdr y))))))
(cond
((= (length ll) 1)
(* (place (car ll)) 2))
(else
(+ (place (car ll)) (place (car (last-pair ll))))))))
(let lp ((i 3))
(if (= i 1000)
(pk 'ok)
(begin
(if (not (= (* 2 i) (analyze i)))
(format #t "~a != (analyze ~a) == ~a~%" (* 2 i) (* 2 i)
(analyze (* 2i))))
(lp (+ i 1)))))
next reply other threads:[~2013-04-08 22:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-08 22:03 Stefan Israelsson Tampe [this message]
2013-04-09 10:24 ` Fun with guile, Erastones + goldbach conjecture Stefan Israelsson Tampe
2013-04-09 19:35 ` Panicz Maciej Godek
2013-04-10 0:18 ` Ian Price
2013-04-10 0:11 ` Ian Price
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: https://www.gnu.org/software/guile/
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1551498.g80VkUsTQo@warperdoze \
--to=stefan.itampe@gmail.com \
--cc=guile-devel@gnu.org \
--cc=guile-user@gnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).