[racket] Calculating cumulative sum of the list

Consider the performance implications. 


On Jan 22, 2015, at 1:59 PM, Jack Firth <jackhfirth at gmail.com> wrote:

> If you're using all of racket, here's a way to do it with heavy usage of higher order functions
> 
> #lang racket
> 
> (define (cumulative-sum xs)
>   (map (curry foldl + 0)
>            (build-list (length xs)
>                            (compose (curry take xs)
>                                             add1))))
> 
> On Thu, Jan 22, 2015 at 6:34 AM, Matthias Felleisen <matthias at ccs.neu.edu> wrote:
> 
> #lang racket
> 
> ;; [Listof Number] -> [Listof Number]
> ;; given (a b c ...) produce (a (+ a b) (+ a b c) ...)
> (define (cumulative-sum l #;"final private:" [so-far 0])
>   (cond
>     [(empty? l) '()]
>     [else (define next (+ so-far (first l)))
>           (cons next (cumulative-sum (rest l) next))]))
> 
> (module+ main
>   (cumulative-sum '(1 2 3)))
> 
> ;; The comments are HtDP-style, but the optional entry parameter is not available in the teaching languages.
> 
> 
> On Jan 22, 2015, at 8:53 AM, Alexandr M <rus314 at gmail.com> wrote:
> 
> > Hello,
> >
> > I am trying to replicate functionality of this code in Python:
> >
> > https://gist.github.com/m-blog/22b7c5d31b3839ffba50#file-cumsum-py
> >
> > in Racket without usage of any libraries.
> >
> > What would the most optimal / concise way to do it in Racket?
> >
> > Thank you.
> >
> > --
> > Best regards,
> > Alex
> > ____________________
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> >  http://lists.racket-lang.org/users
> 
> 
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