RFC: Replace DList with an owned doubly-linked list, Add trait Deque

src/libextra/container.rs

@@ -0,0 +1,40 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Container traits for extra
+
+use std::container::Mutable;
+
+/// A double-ended sequence that allows querying, insertion and deletion at both ends.
+pub trait Deque<T> : Mutable {
+    /// Provide a reference to the front element, or None if the sequence is empty
+    fn front<'a>(&'a self) -> Option<&'a T>;
+
+    /// Provide a mutable reference to the front element, or None if the sequence is empty
+    fn front_mut<'a>(&'a mut self) -> Option<&'a mut T>;
+
+    /// Provide a reference to the back element, or None if the sequence is empty
+    fn back<'a>(&'a self) -> Option<&'a T>;
+
+    /// Provide a mutable reference to the back element, or None if the sequence is empty
+    fn back_mut<'a>(&'a mut self) -> Option<&'a mut T>;
+
+    /// Insert an element first in the sequence
+    fn push_front(&mut self, elt: T);
+
+    /// Insert an element last in the sequence
+    fn push_back(&mut self, elt: T);
+
+    /// Remove the last element and return it, or None if the sequence is empty
+    fn pop_back(&mut self) -> Option<T>;
+
+    /// Remove the first element and return it, or None if the sequence is empty
+    fn pop_front(&mut self) -> Option<T>;
+}