Use a while$-$loop to complete the function. The best approach to implementing this function is to define two variables a and b$,$ where a is $0$ and b is $1.$ Then implement the following rules concerning a and b$.$

$(1)$ if b $>=$ n$,$ stop and let fib $=$ a$.$

$(2)$ else, let a $=$ b and b $=$ a $+$ b $($be careful how you do this; otherwise, you'll get b $=$ b $+$ b$).$ Repeat.

In matlab