CoffeeScript quicksort

qsort.coffee

qsort = (list) ->
  return list if list.length <= 1
  pivotPoint = medianOfThree list
  pivot = list[pivotPoint]
  list.splice pivotPoint, 1, []
  [left, right] = partition list, (e) -> e < pivot
  [(qsort left)..., pivot, (qsort right)...]

medianOfThree = (list) ->
  return 0 if list.length < 3
  fst = list[0]
  mid = list[midPos = Math.floor list.length / 2]
  lst = list[lastPos = list.length - 1]
  # this could instead be done efficiently in 8/3 tests on average
  if fst < mid < lst or lst < mid < fst then midPos
  else if mid < lst < fst or fst < lst < mid then lstPos
  else 0

partition = (list, test = (x) -> x) ->
  pass = []
  fail = []
  for e in list
    (if test e then pass else fail).push e
  [pass, fail]

Very cool. I had to look up the ... syntax because that was new to me. Only iterating the list once is a nice touch too, I left that out for simplicity's sake. Returning a list with named members is still something I'm coming to terms with... cool feature though.