Iterators

1. Iterate over vector of numbers
2. Alternatively, we could create an iterator using the iter method.
3. Count number of elements of an iterator
4. Iterator: all the elements
5. Iteration moves values
6. Iterator that restarts
7. Circular Iterator that restarts
8. Create a simple iterator to count up to a number
9. Create a simple iterator to count boundless
10. Iterate over files in current directory
11. Iterate over files in current directory calling next
12. Iterator to walk directory tree
13. Mutable iterator
14. Exercise: Iterator for the Fibonacci series
15. Solution: Iterator for the Fibonacci series
16. Iter strings