# Beautiful Code, Chapter 6.
# The implementation of binary search that is tested.

# Return the index of an element in a sorted list. (or -1, if not present)
index: (list, target) ->
  [low, high]: [0, list.length]
  while low < high
    mid: (low + high) >> 1
    val: list[mid]
    return mid if val is target
    if val < target then low: mid + 1 else high: mid
  return -1

puts 2 is index([10, 20, 30, 40, 50], 30)
puts 4 is index([-97, 35, 67, 88, 1200], 1200)
puts 0 is index([0, 45, 70], 0)