Loop invariant of linear search

Question

As seen on Introduction to Algorithms (http://mitpress.mit.edu/algorithms), the exercise states the following:

Input: Array A[1..n] and a v

Answer 1

Loop invariant would be

forevery 0 <= i < k, where k is the current value of the loop iteration variable, A[i] != v

On loop termination:

if A[k] == v, then the loop terminates and outputs k

if A[k] != v, and k + 1 == n (size of list) then loop terminates with value nil

Proof of Correctness: left as an exercise