Iterator interfacev0.1.0

pub interface Iterator {}

The compiler drives iteration by shape rather than through this interface: a for loop accepts any type with a func Next(self: &var Self) -> Item?, which advances the cursor and reports either the next item or, with none, that the sequence has ended. The item type is whatever that optional carries, and it differs per iterator, so the method is not written here; the generic Cursor<T> names it for bounds, which is how the adaptors take an iterator. What this interface adds is the name. extend MyCursor : Iterator records that a type means to be an iterator and documents which of its methods carry the protocol, and a bound written <T: Iterator> says what a generic expects of its argument. Neither is required to iterate, and a bound on it grants no operations, so a generic that needs to advance a cursor itself should take the concrete iterator type. An iterator is consumed as it is read: Next mutates it, and an iterator that has reported none keeps reporting none. Nothing here promises an iterator can be restarted or copied. An iterator borrows whatever it walks over. Modifying that container while an iterator over it is alive — growing a vector, rehashing a map, freeing the storage — leaves the iterator pointing at storage that has moved or gone, and reading it afterwards is undefined. Finish with the iterator before touching the container.