Naive implementation of merge sort

merge_sort.rb

require 'pp'

def merge_sort(array,dir = :ask)
  pp array if $VERBOSE
  raise ArgumentError, "direction must be :ask or :desk symbol" unless [:ask,:desk].include? dir
  return array if array.count == 1
  array.reverse!
  middle = array.count / 2
  right, left = array[0...middle].reverse, array[middle..-1].reverse
  pp [left,right] if $VERBOSE
  right, left = merge_sort(right, dir), merge_sort(left, dir)
  merge(left,right,dir)
end

def merge(left,right,dir)
  pp [left,right] if $VERBOSE
  action = case dir
           when :ask
             :<
           when :desk
             :>
           end
  result = []
  until left.empty? or right.empty?
    el = if left.first.send(action,right.first)
           found = left.first
           left.delete(found)
           left.compact!
           found
          else
           found = right.first
           right.delete(found)
           right.compact!
           found
          end
    result << el
    if left.empty?
      return result + right
    elsif right.empty?
      return result + left
    end
  end
end



pp merge_sort(eval(ARGV[0]),eval(ARGV[1]))