4 ms·

I don't understand what your concern is - this only took me about a minute to write and it looks completely safe and efficient. https://play.rust-lang.org/?gis

• GreaterFool 9y ago
  Thanks for this snippet. Didn't think about that. If I understand correctly that's overly restrictive though. You're limiting the lifetime of list elements to the lifetime of the spine of the list. What I want is this: enum List<T> { Nil, Cons(T, Box<List<T>>) } struct IntoIter<T>(List<T>); impl<T> IntoIterator for List<T> { type Item = T; type IntoIter = IntoIter<T>; fn into_iter(self) -> Self::IntoIter { IntoIter(self) } } impl<T> Iterator for IntoIter<T> { type Item = T; fn next(&mut self) -> Option<T> { match std::mem::replace(&mut self.0, List::Nil) { List::Nil => None, List::Cons(x, l) => { std::mem::replace(&mut self.0, *l); Some(x) } } } } But without the `replace` calls. Also, in general I may be working with a data type for which I don't have a value I can conjure out of thin air (like `Nil`). What then?