From: "Kroeger, Simon (ext)" <simon.kroeger.ext@...>
Date: 2006-08-07T23:48:52+09:00
Subject: Re: nextPowerOf2(n)

 

> From: Ch Skilbeck
> Sent: Monday, August 07, 2006 4:30 PM
> 
> 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

def nextPowerOf2(n)
  2 ** (Math.log(n) / Math.log(2)).ceil
end

cheers

Simon