From: Sam Duncan <sduncan@...>
Date: 2011-03-30T05:17:07+09:00
Subject: Re: Why can a floating point number be used as an array index?

How about statistical bucketing. Imagine your indexes 1, 2, and 3 are Gb 
of RSS or something.

 > irb
ruby-1.9.2-p0 > rss = [0.123, 1.223, 5.33, 2.294, 7.66, 5.6, 3.222, 
3.88, 3.44, 1.78] # incoming rss values
  => [0.123, 1.223, 5.33, 2.294, 7.66, 5.6, 3.222, 3.88, 3.44, 1.78]

ruby-1.9.2-p0 > buckets = (0..rss.max).collect {|i| i} # bucket indexes
  => [0, 1, 2, 3, 4, 5, 6, 7]

ruby-1.9.2-p0 > rss.reduce(Hash.new(0)) {|h, v| h.tap{|h| 
h[buckets[v]]+=1}} # statistics!
  => {0=>1, 1=>2, 5=>2, 2=>1, 7=>1, 3=>3}

I'm sure there are lots of (probably simpler) ways to do the same thing, 
but it was a fun exercise nonetheless =]

Sam


On 30/03/11 07:35, Jeff Dik wrote:
> Why can a floating point number be used as an array index?  Anybody
> know of a good use case for this?
>
> irb(main):020:0>  [1, 2, 3][0.3]
> 1
> irb(main):021:0>  [1, 2, 3][0.9]
> 1
>
> Just curious,
> Jeff
>
>