diff --git a/src/libstd/vec.rs b/src/libstd/vec.rs index 1014ff48b1d..7ae4e8a1d2f 100644 --- a/src/libstd/vec.rs +++ b/src/libstd/vec.rs @@ -1091,6 +1091,7 @@ pub trait OwnedVector { fn push_all_move(&mut self, rhs: ~[T]); fn pop(&mut self) -> T; + fn pop_opt(&mut self) -> Option; fn shift(&mut self) -> T; fn unshift(&mut self, x: T); fn insert(&mut self, i: uint, x:T); @@ -1281,18 +1282,26 @@ impl OwnedVector for ~[T] { } } - /// Remove the last element from a vector and return it + /// Remove the last element from a vector and return it, or `None` if it is empty + fn pop_opt(&mut self) -> Option { + match self.len() { + 0 => None, + ln => { + let valptr = ptr::to_mut_unsafe_ptr(&mut self[ln - 1u]); + unsafe { + let val = ptr::replace_ptr(valptr, intrinsics::init()); + raw::set_len(self, ln - 1u); + Some(val) + } + } + } + } + + + /// Remove the last element from a vector and return it, failing if it is empty + #[inline] fn pop(&mut self) -> T { - let ln = self.len(); - if ln == 0 { - fail!("sorry, cannot pop an empty vector") - } - let valptr = ptr::to_mut_unsafe_ptr(&mut self[ln - 1u]); - unsafe { - let val = ptr::replace_ptr(valptr, intrinsics::init()); - raw::set_len(self, ln - 1u); - val - } + self.pop_opt().expect("pop: empty vector") } /// Removes the first element from a vector and return it @@ -2089,18 +2098,13 @@ impl Iterator for VecConsumeIterator { // // [1,2,3,4,5] => 1, [5,2,3,4] => 2, [5,4,3] => 3, [5,4] => 4, // [5] -> 5, [] - - if self.v.is_empty() { - None - } else { - let l = self.v.len(); - if self.idx < l { - self.v.swap(self.idx, l - 1); - self.idx += 1; - } - - Some(self.v.pop()) + let l = self.v.len(); + if self.idx < l { + self.v.swap(self.idx, l - 1); + self.idx += 1; } + + self.v.pop_opt() } } @@ -2111,8 +2115,7 @@ pub struct VecConsumeRevIterator { impl Iterator for VecConsumeRevIterator { fn next(&mut self) -> Option { - if self.v.is_empty() { None } - else { Some(self.v.pop()) } + self.v.pop_opt() } } @@ -2415,6 +2418,17 @@ mod tests { } #[test] + fn test_pop_opt() { + let mut v = ~[5]; + let e = v.pop_opt(); + assert_eq!(v.len(), 0); + assert_eq!(e, Some(5)); + let f = v.pop_opt(); + assert_eq!(f, None); + let g = v.pop_opt(); + assert_eq!(g, None); + } + fn test_swap_remove() { let mut v = ~[1, 2, 3, 4, 5]; let mut e = v.swap_remove(0);