binary_search.rb

def binary_search(target, list)
  # find the middle position number
  position = (list.count / 2).floor

  # look up the item in the middle position
  mid = list[position]

  # if we've found it, we're done
  return mid if mid == target

  if(mid < target)
    # mid is less than the target meaning we should continue the process 
    # on the right half, meaning starting at the position + 1 to the end 
    # of the list
    return binary_search(target, list.slice(position + 1, list.count/2))
  else
    # mid is greater than the target, meaning we should start
    # at the beginning of the list, and eliminate the stuff
    # on the right hand side.
    return binary_search(target, list.slice(0, list.count/2))
  end
end


puts binary_search(9, [1,2,3,4,5,6,7,8,9,10])