From: Sebastian Hungerecker <sepp2k@...>
Date: 2008-09-21T18:37:34+09:00
Subject: Re: One-Liners Mashup (#177 again)

James Coglan wrote:
> def per(n, p = 16)
>   (1..(p/2)).detect { |x| ("%.#{p}f" %
> (1.0/n)).split(".").last.scan(%r{.{#{x}}}).uniq.size == 1 } || 0
> end
>
> This produces correct output for the numbers you specified.

It produces 0 for 6 though (because printf rounds instead of truncating so you 
get a 7 at the end).
Here's one that should always be accurate and it's even in 1 line and handles 
different bases:
def per(n, b = 10)
  i=1;x=b;h={};loop {x=x%n*b;break 0 if x==0;h[x]?(break i-h[x]):h[x]=i; i+=1}
end

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