From: hadley wickham <h.wickham@...>
Date: 2006-08-08T01:07:16+09:00
Subject: Re: nextPowerOf2(n)

> Here's another take
>
> irb(main):016:0> class Fixnum
> irb(main):017:1>     def next_power_of_2
> irb(main):018:2>       trial = 1
> irb(main):019:2>       trial <<= 1 while trial < self
> irb(main):020:2>       return trial
> irb(main):021:2>     end
> irb(main):022:1> end
> => nil
> irb(main):023:0> (-1..10).collect { | i | [i, i.next_power_of_2] }
> => [[-1, 1], [0, 1], [1, 1], [2, 2], [3, 4], [4, 4], [5, 8], [6, 8],
> [7, 8], [8, 8], [9, 16], [10, 16]]
> irb(main):024:0>
>
> This should be fairly fast since at first glance it's o(log2(n))

When the alternatives are O(1), that's not that great!

Hadley