[plt-dev] Racket web page

Doesn't Matthias's version return #t and Matthew's returns void? (void
being preferable because it doesn't print anything?)

Robby

On Wed, May 26, 2010 at 9:27 AM, Matthias Felleisen
<matthias at ccs.neu.edu> wrote:
>
> On May 25, 2010, at 8:48 PM, Matthew Flatt wrote:
>
>> #lang racket
>> ;; Report each unique line from stdin:
>> (let ([saw (make-hash)])
>>   (for ([line (in-lines)])
>>     (unless (hash-ref saw line #f)
>>       (displayln line))
>>     (hash-set! saw line #t)))
>
> I would prefer to sacrifice one line to avoid the repetition of the test (leakage). I doubt Perl and friends do that:
>
> #lang racket
> ;; Report each unique line from stdin:
> (define saw (make-hash))
> (for ([line (in-lines)])
>  (hash-ref saw line
>    (lambda ()
>      (displayln line)
>      (hash-set! saw line #t))))
>
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