[racket] A question about code-style (and memory usage)

Hi Rodolfo,

I think solution 2 is generally preferred, and
solution 1 would be considered a slight abuse of apply.

On the other hand, I find that summing comes up sufficiently
often to deserve its own compact syntax, so I propose:

;; Solution 3
(require (planet "mathsymbols.rkt" ("stephanh" "mathsymbols.plt" 1 0)))

(Σ ([i (in-range 1 (add1 N))])
        (string-length (integer->string i)))

Stephan


On 07/24/2011 06:25 AM, Rodolfo Carvalho wrote:
> Some days ago I came across Williams' describe <http://planet.racket-lang.org/display.ss?package=describe.plt&owner=williams> collection from PLaneT. That's pretty awesome.
> And coincidentally came this problem <http://projecteuler.net/index.php?section=problems&id=17> from Project Euler.
>
> Then I wrote two solutions, and I was wondering which one of them have the best style, according to Racket's philosophy.
>
> #lang racket
> (require (planet williams/describe/describe))
>
> (define N 1000)
>
> ;; Solution 1
> (apply + (build-list N (compose string-length integer->string add1)))
>
> ;; Solution 2
> (for/fold ([sum 0])
>    ([i (in-range 1 (add1 N))])
>    (+ sum ((compose string-length integer->string) i)))
>
>
>
> For me solution 1 is compact, however it allocates the list without need (which gives out of memory error for large N). Solution 2 is more memory efficient, but more verbose.
>
>
> BTW what's the recommended way to check "per-function" memory usage? There's an unanswered question about memory profiling
> <http://groups.google.com/group/racket-users/browse_thread/thread/d48ce09209a5aea4> in the mailing list, and I could find my way out searching PLaneT, the docs and the
> mailing list archive.
>
>
> []'s
>
> Rodolfo Carvalho
>
>
>
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