solution to project euler no.14

pe14.rb

#!/usr/bin/ruby
class PE14
  @@l=Hash.new
  @@l[1]=1
  def PE14.eval x
    if @@l[x]      #found
      return @@l[x]
    else
      if x%2==0   #even
        y=PE14.eval(x/2)
      else        #old
        y=PE14.eval(1+3*x)
      end
      @@l[x]=y+1
    end
  end
end

p (1..1000000).max_by {|x| PE14.eval x}