If calling max() changed the sequence, max does not change a sequence, it consumes the iterator. I would expect it would have to be declared as mutable max t

If calling max() changed the sequence, max does not change a sequence, it consumes the iterator. I would expect it would have to be declared as mutable max takes self (and not &self), so the ownership of the iterator is moved to the max method. The new owner can decide to bind the value mutably. This is always the case when a value is moved and changes ownership, e.g.: https://play.rust-lang.org/?gist=50e6fe86e530baeabda1a7cca3c785ab&version=stable&mode=debug&edition=2015 https://play.rust-lang.org/?gist=50e6fe86e530baeabda1a7cca3c...