Sorry, forgot to attach the test suite. [email protected] <[email protected]> 於 2020年8月5日 週三 下午11:21寫道：
> I was working on a exercism problem named Raindrops. > > Problem description: > Convert a number to a string, the contents of which depend on the number's > factors. > > If the number has 3 as a factor, output 'Pling'. > If the number has 5 as a factor, output 'Plang'. > If the number has 7 as a factor, output 'Plong'. > If the number does not have 3, 5, or 7 as a factor, just pass the number's > digits straight through. > > I came out with two version. > > ; version 1 > (define (convert n) > (define pling (divides? 3 n)) > (define plang (divides? 5 n)) > (define plong (divides? 7 n)) > (if (or pling plang plong) > (string-append (if pling "Pling" "") > (if plang "Plang" "") > (if plong "Plong" "")) > (number->string n))) > > ; version 2 > (define (convert n) > (define table '((3 . "Pling") (5 . "Plang") (7 . "Plong"))) > (define result (for/list ([(k v) (in-dict table)] #:when (divides? k n)) > v)) > (if (empty? result) (number->string n) > (string-append* result))) > > (require math/number-theory) > > I thought version 1 would be faster, but it turned out to be wrong. > Running with raco test got following timing information. > > version 1 > cpu time: 9 real time: 9 gc time: 9 > version 2 > cpu time: 0 real time: 0 gc time: 0 > > Then I ran both version in DrRacket, both output following result. > cpu time: 0 real time: 0 gc time: 0 > > It's strange, isn't it? > > -- > You received this message because you are subscribed to a topic in the > Google Groups "Racket Users" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/racket-users/LhCM51vnywg/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/racket-users/46592171-c357-4897-af1a-bea91c838cacn%40googlegroups.com > <https://groups.google.com/d/msgid/racket-users/46592171-c357-4897-af1a-bea91c838cacn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- - sleepnova 呼叫小黃創辦人 & CEO -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/CABa2-7MsirGY2p7ib%3D7a6Nb%3D49%2BW%3DK3uReJvepc_fqs0NbSmQw%40mail.gmail.com.
raindrops-test.rkt
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