#!/usr/bin/env ruby

class Array
  def sum
    reduce(0) { |s, i| s += i }
  end

  def avg
    empty? ? 0.0 : sum.to_f / size
  end

  def var
    empty? ? 0.0 : map { |x| x ** 2 }.avg - avg ** 2
  end
end

# All of these should clearly return 0.

p [1295218865, 1295218865, 1295218865, 1295218865, 1295218865].var
#=> 0.0

p [1295218865, 1295218865, 1295218865, 1295218865, 1295218865, 1295218865].var
#=> 256.0

p [1295218865, 1295218865, 1295218865, 1295218865, 1295218865, 1295218865, 1295218865].var
#=> 0.0