[Haskell-cafe] Style
Marc A. Ziegert
coeus at gmx.de
Sat Aug 25 01:34:10 EDT 2007
whops... i did check it, but
that was a copypaste mistake.
buggy:
> tm_parallelizable_v1 = \n -> sum . takeWhile (>0) $ map (div n) fives
> where fives = iterate (*5) 1
should be:
> tm_parallelizable_v1 = \n -> sum . takeWhile (>0) $ map (div n) fives
> where fives = iterate (*5) 5
- marc
Am Freitag, 24. August 2007 schrieben Sie:
> Hi Marc
>
> First off, thanks for your reply.
> >> tm_parallelizable_v1 = \n -> sum . takeWhile (>0) $ map (div n) fives
> >> where fives = iterate (*5) 1
> Did you check this one? IMHO I think it's producing the 'wrong' answer.
>
> *Main> tm_parallelizable_v1 100
> 124
> (0.00 secs, 0 bytes)
>
> *Main> tm 100
> 24
> (0.00 secs, 0 bytes)
>
> If comparing the result to the other variants is accepted as a sort
> of proof. ;-)
>
> But calculating the number of trailing zero's of n! is a matter of
> counting powers of five in the factorized n!: f.e.:
>
> 10! = 1 2 3 2^2 5 2*3 7 2^3 3^2 2*5
> --> 5^2 --> picking up enough powers of 2 --> (2*5)^2 = 100
>
> So you will have to correct your 'fives' to f.e.
>
> fives = tail $ iterate (*5) 1
>
>
>
> Regards
>
>
> @@i
>
>
>
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