input: Write a function to implement a binary search algorithm that efficiently finds an item in a sorted list of items. The function should return the index of the item if found, otherwise return -1.
  
  def binary_search(nums, val):
      low = 0
      high = len(nums) - 1
      
      while low <= high:
          mid = (low + high) // 2
          if nums[mid] == val:
              return mid
          elif nums[mid] > val:
              high = mid - 1
          else:
              low = mid + 1
      return -1
  
  assert binary_search([3, 4, 5, 6, 7, 8, 9], 8) == 5
  assert binary_search([3, 4, 5, 6, 7, 8, 9], 10) == -1
  assert binary_search([], 8) == -1
  assert binary_search([1, 2, 3, 4, 5], 3) == 2
  assert binary_search([1, 2, 3, 4, 5], 1) == 0
output: def binary_search(nums, val):
      low = 0
      high = len(nums) - 1
      
      while low <= high:
          mid = (low + high) // 2
          if nums[mid] == val:
              return mid
          elif nums[mid] > val:
              high = mid - 1
          else:
              low = mid + 1
      return -1