binary search middle value calculation

Question

The following is the pseudocode I got from a TopCoder tutorial about binary search

binary_search(A, target):
   lo = 1, hi = size(A)
   while lo <= hi:
               


        

Answer 1

From later on in the same tutorial:

"You may also wonder as to why mid is calculated using mid = lo + (hi-lo)/2 instead of the usual mid = (lo+hi)/2. This is to avoid another potential rounding bug: in the first case, we want the division to always round down, towards the lower bound. But division truncates, so when lo+hi would be negative, it would start rounding towards the higher bound. Coding the calculation this way ensures that the number divided is always positive and hence always rounds as we want it to. Although the bug doesn't surface when the search space consists only of positive integers or real numbers, I've decided to code it this way throughout the article for consistency."