fib

fib

Write an implementation of the fibonacci function.

The fibonacci function is defined as follows:

It is a function that takes one parameter, n
and returns the nth number in the fibonacci sequence.
The fibonacci sequence is the sequence of numbers,
beginning with zero and then one, where all succeeding
numbers in the sequence are the sum of the previous two
numbers.

i.e.:
n    fib(n)
0    0    as defined
1    1    as defined
2    1  = 0 + 1
3    2  = 1 + 1
4    3  = 1 + 2
5    5  = 2 + 3
6    8  = 3 + 5