From: Erik Veenstra <erikveen@...>
Date: 2008-10-01T20:29:32+09:00
Subject: Re: Mode method for Array

And since we all love speed, we tend to avoid inject. (For
those who don't know: inject and inject! are really, really
slow. I mean, _really_ slow...)

Speed is also the reason for "pre-defining" variables used in
iterations. (6% faster!!)

For low level methods like these, speed is much more important
than readability. And the inject versions of the methods below
aren't even more readable than the faster implementations.

So, we'll go for the fast ones:

 module Enumerable
   def mode
     empty? ? [] : frequencies.group_by_value.max.last
   end

   def frequencies
     x   = nil
     res = Hash.new(0)
     each{|x| res[x] += 1}
     res
   end
 end

 class Hash
   def group_by_value
     k   = v = nil
     res = {}
     each{|k, v| (res[v] ||= []) << k}
     res
   end
 end

gegroet,
Erik V. - http://www.erikveen.dds.nl/