Iterators
The Iterator trait is used to implement iterators over collections such as arrays.
The trait requires only a method to be defined for the next element,
which may be manually defined in an impl block or automatically
defined (as in arrays and ranges).
As a point of convenience for common situations, the for construct
turns some collections into iterators using the .into_iterator() method.
Methods that can be accessed using the Iterator trait in addition
to those shown in the example below can be found here.