jashkenas--coffeescript/examples/computer_science/merge_sort.coffee

# Sorts an array in ascending natural order using merge sort.
merge_sort: (list) ->

  return list if list.length is 1

  result: []
  pivot: Math.floor(list.length / 2)
  left:  merge_sort(list.slice(0, pivot))
  right: merge_sort(list.slice(pivot))

  while left.length and right.length
    result.push(if left[0] < right[0] then left.shift() else right.shift())

  result.concat(left).concat(right)


# Test the function.
puts(merge_sort([3, 2, 1]).join(' ') is '1 2 3')
puts(merge_sort([9, 2, 7, 0, 1]).join(' ') is '0 1 2 7 9')