function binary_search(sorted_items, target):

 low = 0
 high = length(sorted_items) - 1
 while low <= high:
 middle = (low + high) // 2
 if sorted_items[middle] == target:
 return middle

 if sorted_items[middle] < target:
 low = middle + 1
 else:
 high = middle - 1
 return not_found
