Hi Tim, Thanks for sharing your code.
Quick, newby question: why do you use "and" instead of "begin" in your progress function? I've seen others do this as well (of course, Eli's "(and...)" idiom above is a whole different animal... and very cool. Thanks, -Joe On Wed, Mar 21, 2012 at 10:01 AM, Tim Brown <tim.br...@cityc.co.uk> wrote: > Rodolfo, > > I started Project Euler with nested (do ...) loops. > Which are beyond ugly. It was truly revolutionary > finding the for/... forms. > > Get a hang of them! > > Also, you might like to use: > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;**;;;;;;;;;;;;;;;;;;; > (define last-progress-ms #f) > ;;; it's global, it's expeident, but it has worked for me so far! > (define (progress i period (max-i #f)) > (when (= (modulo i period) 0) > (let* ((now-ms (current-milliseconds)) > (delta-raw (and last-progress-ms (- now-ms last-progress-ms))) > (delta-s (and delta-raw (quotient delta-raw 1000))) > (delta-ms (and delta-raw (remainder delta-raw 1000)))) > (set! last-progress-ms now-ms) > (if > max-i > (and > (printf "~a+~a:~a.~a|" i (- max-i i) delta-s delta-ms) > (flush-output)) > (and (printf "~a:~a.~a|" (/ i period) delta-s delta-ms) > (flush-output)))))) > ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;**;;;;;;;;;;;;;;;;;;; > > It's useful in loops like: > > (let ((stupid-number-youll-find-so-**often-in-PE(expt 10 1034))) > (for*/first > ( > [k (in-range 0 stupid-number-youll-find-so-**often-in-PE)] > #:when (progress (- stupid-number-youll-find-so-**often-in-PE k) > 1000000) > [i (in-range 0 10)] > [j (in-range 0 10)] > ...))) > > You'll know when you'll need it! > #:when (printf ...) > will become your friend! > > Tim > > > Eli Barzilay wrote: > >> 20 minutes ago, Rodolfo Carvalho wrote: >> >>> >>> (define (pythagorean-triple/alt n) >>> (for*/first ([a (in-range 1 n)] >>> [b (in-range a n)] >>> [c (in-value (- n a b))] >>> #:when (right-triangle? a b c)) >>> (list a b c))) >>> >> >> You can also use `for*/or': >> >> (define (pythagorean-triple/alt n) >> (for*/or ([a (in-range 1 n)] >> [b (in-range a n)]) >> (define c (- n a b)) >> (and (right-triangle? a b c) (list a b c)))) >> >> > > -- > Tim Brown <tim.br...@cityc.co.uk> | City Computing Limited | > T: +44 20 8770 2110 | City House, Sutton Park Road | > F: +44 20 8770 2130 | Sutton, Surrey, SM1 2AE, GB | > ------------------------------**------------------------------** > -----------| > BEAUTY: What's in your eye when you have a bee in your hand | > ------------------------------**------------------------------** > -----------' > City Computing Limited registered in London No. 1767817. > Registered Office: City House, Sutton Park Road, Sutton, Surrey, SM1 2AE > VAT number 372 8290 34. > > ____________________ > Racket Users list: > http://lists.racket-lang.org/**users <http://lists.racket-lang.org/users> >
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