You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: median.rb
    path of file: ./repos/facets/lib/standard/facets/math
    
    the code of the file until where you have to start completion: require 'facets/math/percentile'

module Math

  # Returns the numerical median for the an array of values;
  # or nil if array is
    
  def self.median(array)
    return 0 if array.size == 0

    tmp = array.sort
    mid = tmp.size / 2

    if (tmp.size % 2) == 0
	    (tmp[mid-1] + tmp[mid]).to_f / 2
    else
	    tmp[mid]
    end