diff options
| -rw-r--r-- | library/alloc/src/collections/linked_list.rs | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/library/alloc/src/collections/linked_list.rs b/library/alloc/src/collections/linked_list.rs index 052edf453f6..3bfbd1d9d2d 100644 --- a/library/alloc/src/collections/linked_list.rs +++ b/library/alloc/src/collections/linked_list.rs @@ -1024,6 +1024,99 @@ impl<T, A: Allocator> LinkedList<T, A> { } } + /// Retains only the elements specified by the predicate. + /// + /// In other words, remove all elements `e` for which `f(&e)` returns false. + /// This method operates in place, visiting each element exactly once in the + /// original order, and preserves the order of the retained elements. + /// + /// # Examples + /// + /// ``` + /// #![feature(linked_list_retain)] + /// use std::collections::LinkedList; + /// + /// let mut d = LinkedList::new(); + /// + /// d.push_front(1); + /// d.push_front(2); + /// d.push_front(3); + /// + /// d.retain(|&x| x % 2 == 0); + /// + /// assert_eq!(d.pop_front(), Some(2)); + /// assert_eq!(d.pop_front(), None); + /// ``` + /// + /// Because the elements are visited exactly once in the original order, + /// external state may be used to decide which elements to keep. + /// + /// ``` + /// #![feature(linked_list_retain)] + /// use std::collections::LinkedList; + /// + /// let mut d = LinkedList::new(); + /// + /// d.push_front(1); + /// d.push_front(2); + /// d.push_front(3); + /// + /// let keep = [false, true, false]; + /// let mut iter = keep.iter(); + /// d.retain(|_| *iter.next().unwrap()); + /// assert_eq!(d.pop_front(), Some(2)); + /// assert_eq!(d.pop_front(), None); + /// ``` + #[unstable(feature = "linked_list_retain", issue = "114135")] + pub fn retain<F>(&mut self, mut f: F) + where + F: FnMut(&T) -> bool, + { + self.retain_mut(|elem| f(elem)); + } + + /// Retains only the elements specified by the predicate. + /// + /// In other words, remove all elements `e` for which `f(&e)` returns false. + /// This method operates in place, visiting each element exactly once in the + /// original order, and preserves the order of the retained elements. + /// + /// # Examples + /// + /// ``` + /// #![feature(linked_list_retain)] + /// use std::collections::LinkedList; + /// + /// let mut d = LinkedList::new(); + /// + /// d.push_front(1); + /// d.push_front(2); + /// d.push_front(3); + /// + /// d.retain_mut(|x| if *x % 2 == 0 { + /// *x += 1; + /// true + /// } else { + /// false + /// }); + /// assert_eq!(d.pop_front(), Some(3)); + /// assert_eq!(d.pop_front(), None); + /// ``` + #[unstable(feature = "linked_list_retain", issue = "114135")] + pub fn retain_mut<F>(&mut self, mut f: F) + where + F: FnMut(&mut T) -> bool, + { + let mut cursor = self.cursor_front_mut(); + while let Some(node) = cursor.current() { + if !f(node) { + cursor.remove_current().unwrap(); + } else { + cursor.move_next(); + } + } + } + /// Creates an iterator which uses a closure to determine if an element should be removed. /// /// If the closure returns true, then the element is removed and yielded. |