Practice while-loops

Write a function called next_prime that takes a scalar positive integer input n. Use a while-loop to find and return k, the smallest prime number that is greater than n. Feel free to use the built-in isprime function. Here are some example runs:

>> next_prime(2)
ans =
     3
>> next_prime(8)
ans =
    11
>> next_prime(12345678)
ans =
    12345701