diff options
| -rw-r--r-- | src/libcollections/dlist.rs | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/src/libcollections/dlist.rs b/src/libcollections/dlist.rs index a080146e0ec..abe206c3914 100644 --- a/src/libcollections/dlist.rs +++ b/src/libcollections/dlist.rs @@ -560,7 +560,12 @@ impl<T> DList<T> { /// Splits the list into two at the given index. Returns everything after the given index, /// including the index. /// + /// # Panics + /// + /// Panics if `at > len`. + /// /// This operation should compute in O(n) time. + /// /// # Examples /// /// ``` @@ -580,9 +585,11 @@ impl<T> DList<T> { #[stable(feature = "rust1", since = "1.0.0")] pub fn split_off(&mut self, at: usize) -> DList<T> { let len = self.len(); - assert!(at < len, "Cannot split off at a nonexistent index"); + assert!(at <= len, "Cannot split off at a nonexistent index"); if at == 0 { return mem::replace(self, DList::new()); + } else if at == len { + return DList::new(); } // Below, we iterate towards the `i-1`th node, either from the start or the end, @@ -1116,6 +1123,18 @@ mod tests { } } + // no-op on the last index + { + let mut m = DList::new(); + m.push_back(1); + + let p = m.split_off(1); + assert_eq!(m.len(), 1); + assert_eq!(p.len(), 0); + assert_eq!(m.back(), Some(&1)); + assert_eq!(m.front(), Some(&1)); + } + } #[test] |