Implement PartialOrd for RingBuf

Author: nham

src/libcollections/ringbuf.rs

@@ -19,6 +19,7 @@ use core::cmp;
 use core::default::Default;
 use core::fmt;
 use core::iter::RandomAccessIterator;
+use core::iter;
 use std::hash::{Writer, Hash};
 
 use {Deque, Collection, Mutable, MutableSeq};
@@ -451,6 +452,12 @@ impl<A: PartialEq> PartialEq for RingBuf<A> {
     }
 }
 
+impl<A: PartialOrd> PartialOrd for RingBuf<A> {
+    fn partial_cmp(&self, other: &RingBuf<A>) -> Option<Ordering> {
+        iter::order::partial_cmp(self.iter(), other.iter())
+    }
+}
+
 impl<S: Writer, A: Hash<S>> Hash<S> for RingBuf<A> {
     fn hash(&self, state: &mut S) {
         for elt in self.iter() {
@@ -940,6 +947,19 @@ mod tests {
       assert!(hash::hash(&x) == hash::hash(&y));
     }
 
+    #[test]
+    fn test_ord() {
+        let x = RingBuf::new();
+        let mut y = RingBuf::new();
+        y.push(1i);
+        y.push(2);
+        y.push(3);
+        assert!(x < y);
+        assert!(y > x);
+        assert!(x <= x);
+        assert!(x >= x);
+    }
+
     #[test]
     fn test_show() {
         let ringbuf: RingBuf<int> = range(0i, 10).collect();