From: Christer Nilsson <janchrister.nilsson@...>
Date: 2006-06-04T07:39:09+09:00
Subject: Re: Where can one find examples of masterful Ruby code?

Logan Capaldo wrote:
> On Jun 3, 2006, at 4:48 PM, Alder Green wrote:
> 
>> For example: check if integer i is a power of 2, with an expression no
>> more than 13 characters long.
>>
>> Solution: (i & (i - 1))
> 
> I'm confused.
> 
> 
> irb(main):001:0> i = 9
> => 9
> irb(main):002:0> (i & (i - 1))
> => 8
> 
> So 9 is a power of 2?
> 
> As far as 13 characters goes
> 
> (i % 2).zero?
> 
> is _exactly_ 13 characters and it gives a true or false answer
> instead of zero of something else.

Actually you have to compare with zero to get the expected result as
a previous poster posted:

  def powerof2?( i )
    (i&(i-1))==0
  end

(i&(i-1))==0 counts to twelve characters.

i%2 determines odd or even.

powerof2?(9) => false
powerof2?(16) => true


/christer

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