wavelet.rb

def haar l
  def aux l, m, n
    if l.size == 1
      l + n
    elsif  l.size == 0
      aux m, [], n
    elsif l.size > 1
      aux l[2..-1] , [l[0] + l[1]] + m, [l[0] - l[1]] + n
    else
      []
    end
  end
  aux l, [], []
end

p ary = (1..10).map{ rand(100) }
#ary = [-1, 2]
p ary.inject(:+)
p haar(ary)