I don't see how your function count-times implements the required algorithm.
Please explain. On Mon, May 27, 2013 at 12:01 AM, Tomás Coiro <[email protected]> wrote: > I'm trying to do this Rosetta Code problem: > http://rosettacode.org/wiki/Average_loop_length > > Now, this is my code > #lang racket > (require (only-in math factorial)) > > (define (analytical n) > (apply + > (build-list n (compose (lambda (x) (/ (factorial n) > (expt n x) > (factorial (- n x)))) > add1)))) > > (define (count-times x times) > (if (= 0 (random x)) > (add1 times) > (count-times x (add1 times)))) > > (define (test n times) > (/ > (for/fold ((count 0)) > ((i (in-range times))) > (count-times n count)) > times)) > > (define (test-table max-n times) > (displayln " n\tavg\ttheory\terror") > (displayln "-------------------------------") > (for ((i (in-range 1 (add1 max-n)))) > (define average (exact->inexact (test i times))) > (define theory (exact->inexact (analytical i))) > (define difference (* (sub1 (/ average theory)) 100)) > (displayln (format "~a\t~a\t~a\t~a%" i average theory difference)))) > > (test-table 20 100000) > > > > Im not really worrying about the formatting of the output now, this is the > result. > n avg theory error > ------------------------------- > 1 1.0 1.0 0.0% > 2 2.00036 1.5 33.35733333333335% > 3 3.00578 1.8888888888888888 59.12952941176472% > 4 4.00412 2.21875 80.46738028169015% > 5 5.0035 2.5104 99.31086679413636% > 6 6.00016 2.7746913580246915 116.24603337041157% > 7 7.01433 3.018138700711438 132.4058201283651% > 8 7.9905 3.2450180053710937 146.23900350550514% > 9 8.97363 3.4583157448856556 159.47977749778022% > 10 10.03618 3.66021568 174.19641019624285% > 11 10.97729 3.852372050737359 184.94885373023365% > 12 11.96714 4.036073675098951 196.50449826604333% > 13 12.96795 4.21234791295252 207.8556251283266% > 14 13.99396 4.382029424383519 219.34883691404528% > 15 15.09822 4.545807285147228 232.13506541140143% > 16 15.97676 4.704258247072678 239.62336166263555% > 17 16.99324 4.857870820801628 249.8083960412072% > 18 18.00859 5.007063098992893 259.6637318914995% > 19 18.941 5.152196200957448 267.62963329075353% > 20 20.05709 5.2935845860009 278.8942950499325% > > > the average loop length is too long, I'm worrying if the problem is my code > or if it actually is Windows 8. > I already got a different result with inexact numbers here: > http://rosettacode.org/wiki/Percentage_difference_between_images#Racket > > My question would be first, is my code wrong? (mainly "count-times") > If it isn't, do you guys get similar results? Could there be a bug in the > windows 32-bit installation for Windows 8? > > ____________________ > Racket Users list: > http://lists.racket-lang.org/users > ____________________ Racket Users list: http://lists.racket-lang.org/users
