From: Farrel Lifson <farrel.lifson@...>
Date: 2006-08-07T23:49:54+09:00
Subject: Re: nextPowerOf2(n)

On 07/08/06, Ch Skilbeck <ruby@skilbeck.com> wrote:
> Hi,
>
> Can someone tell me if there's a better way to do this? It takes a
> number and returns the next power of 2 up (or the original if it was
> already a power of 2) Specifically, are there features of Ruby that I
> should be using in this case?
>
> Cheers,
> Charlie.
>
> def nextPowerOf2(n)
>   raise "integer please" if !n.kind_of? Integer
>   high = 0
>   count = 0
>   (0..n.size * 8 - 2).each {|b| count += n[b] ; high = b if n[b] != 0}
>   1 << high + (count > 1 ? 1 : 0)
> end
>
>
> --
> Posted via http://www.ruby-forum.com/.
>
>

My attempt:

# Finds the log base 2 of a number
def Math.log2(n)
  Math.log(n)/Math.log(2)
end

def nextPowerOf2(n)
  if Math.sqrt(n).modulo(1).zero?
    n
  else
    2**Math.log2(5).to_i.succ
  end
end

 Farrel