diff options
| -rw-r--r-- | src/libextra/dlist.rs | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/src/libextra/dlist.rs b/src/libextra/dlist.rs index 9e8982ecf8d..189f20c9740 100644 --- a/src/libextra/dlist.rs +++ b/src/libextra/dlist.rs @@ -258,6 +258,26 @@ impl<T> DList<T> { DList{list_head: None, list_tail: Rawlink::none(), length: 0} } + /// Move the last element to the front of the list. + /// + /// If the list is empty, do nothing. + #[inline] + pub fn rotate_to_front(&mut self) { + do self.pop_back_node().map_consume |tail| { + self.push_front_node(tail) + }; + } + + /// Move the first element to the back of the list. + /// + /// If the list is empty, do nothing. + #[inline] + pub fn rotate_to_back(&mut self) { + do self.pop_front_node().map_consume |head| { + self.push_back_node(head) + }; + } + /// Add all elements from `other` to the end of the list /// /// O(1) @@ -689,6 +709,29 @@ mod tests { } #[test] + fn test_rotate() { + let mut n = DList::new::<int>(); + n.rotate_to_back(); check_links(&n); + assert_eq!(n.len(), 0); + n.rotate_to_front(); check_links(&n); + assert_eq!(n.len(), 0); + + let v = ~[1,2,3,4,5]; + let mut m = list_from(v); + m.rotate_to_back(); check_links(&m); + m.rotate_to_front(); check_links(&m); + assert_eq!(v.iter().collect::<~[&int]>(), m.iter().collect()); + m.rotate_to_front(); check_links(&m); + m.rotate_to_front(); check_links(&m); + m.pop_front(); check_links(&m); + m.rotate_to_front(); check_links(&m); + m.rotate_to_back(); check_links(&m); + m.push_front(9); check_links(&m); + m.rotate_to_front(); check_links(&m); + assert_eq!(~[3,9,5,1,2], m.consume_iter().collect()); + } + + #[test] fn test_iterator() { let m = generate_test(); for m.iter().enumerate().advance |(i, elt)| { |