{"action":"opened","issue":{"url":"https://api.github.com/repos/rust-lang/rust/issues/30633","labels_url":"https://api.github.com/repos/rust-lang/rust/issues/30633/labels{/name}","comments_url":"https://api.github.com/repos/rust-lang/rust/issues/30633/comments","events_url":"https://api.github.com/repos/rust-lang/rust/issues/30633/events","html_url":"https://github.com/rust-lang/rust/issues/30633","id":124315375,"number":30633,"title":"Clarify iterator protocol and .next_back()","user":{"login":"bluss","id":3209739,"avatar_url":"https://avatars.githubusercontent.com/u/3209739?v=3","gravatar_id":"","url":"https://api.github.com/users/bluss","html_url":"https://github.com/bluss","followers_url":"https://api.github.com/users/bluss/followers","following_url":"https://api.github.com/users/bluss/following{/other_user}","gists_url":"https://api.github.com/users/bluss/gists{/gist_id}","starred_url":"https://api.github.com/users/bluss/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/bluss/subscriptions","organizations_url":"https://api.github.com/users/bluss/orgs","repos_url":"https://api.github.com/users/bluss/repos","events_url":"https://api.github.com/users/bluss/events{/privacy}","received_events_url":"https://api.github.com/users/bluss/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-12-30T07:40:14Z","updated_at":"2015-12-30T07:40:14Z","closed_at":null,"body":"The iterator protocol documents that behavior after calling `.next()` is open to decide for the implementation. We should clarify in `DoubleEndedIterator` that `.next_back()` is to be understood in the same way, and that calls to `next` and `next_back` are interchangeable — any of the two may return `None`, and after that point, the iteration is done the same way."}}