Gnarly quicksort method to be written in Go

gnarly_quicksort.rb

$ cat qs.rb
#
# How the merge sort is to be written for a Coursera course I am taking

@comps = 0
@stack = 0
def qs(a = [], l = 0, r = nil)

  #puts "@stack = #{@stack += 1}"

  pivot = a[l]
  r ||= a.length

  #puts "going to work on: #{a[l..r]}"
  comparisons = (r - l)

  return if comparisons <= 1

  @comps += (comparisons - 1)

  i = l + 1 # Between less than, greater than pivot
  (l+1...r).each do |j|
    if a[j] < pivot
      a[i], a[j] = a[j], a[i]
      i += 1
    end
  end
  a[l], a[i-1] = a[i-1], a[l]


  p a[l,(i-1-l)]
  p a[i, a.length - 1]

  qs a, l, (i-1-l)
  qs a, i+1, a.length - i
end

ary = []
#while line = gets
#  ary << line.to_i
#end
#
ary = 10.times.map { rand(100) }

p ary.length
qs ary
puts "swapping..."
puts "total comparisons: #{@comps}"
puts "total stack frames: #{@stack}"

p ary.first(30), ary.last(30)