---

yaml
---
r: 54671
b: refs/heads/snap-stage3
c: 85b82c7
h: refs/heads/master
i:
  54669: 1260a5f
  54667: 6cd0206
  54663: 939bbb9
  54655: 1b6cb6d
v: v3

Author: huonw

[refs]

@@ -1,7 +1,7 @@
 ---
 refs/heads/master: 5f13e9ccc2e3328d4cd8ca49f84e6840dd998346
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
-refs/heads/snap-stage3: 3698ea7e54c46cfde377f95782710ee5e19876d3
+refs/heads/snap-stage3: 85b82c763bfbfd5de59f4c6b026dca58f3ba4687
 refs/heads/try: 8eb2bab100b42f0ba751552d8eff00eb2134c55a
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/heads/ndm: f3868061cd7988080c30d6d5bf352a5a5fe2460b

branches/snap-stage3/src/libcore/cmp.rs

@@ -116,6 +116,19 @@ totalord_impl!(i64)
 totalord_impl!(int)
 totalord_impl!(uint)
 
+/**
+Return `o1` if it is not `Equal`, otherwise `o2`. Simulates the
+lexical ordering on a type `(int, int)`.
+*/
+// used in deriving code in libsyntax
+#[inline(always)]
+pub fn lexical_ordering(o1: Ordering, o2: Ordering) -> Ordering {
+    match o1 {
+        Equal => o2,
+        _ => o1
+    }
+}
+
 /**
 * Trait for values that can be compared for a sort-order.
 *
@@ -184,6 +197,8 @@ pub fn max<T:Ord>(v1: T, v2: T) -> T {
 
 #[cfg(test)]
 mod test {
+    use super::lexical_ordering;
+
     #[test]
     fn test_int_totalord() {
         assert_eq!(5.cmp(&10), Less);
@@ -204,4 +219,16 @@ mod test {
         assert!(Less < Equal);
         assert_eq!(Greater.cmp(&Less), Greater);
     }
+
+    #[test]
+    fn test_lexical_ordering() {
+        fn t(o1: Ordering, o2: Ordering, e: Ordering) {
+            assert_eq!(lexical_ordering(o1, o2), e);
+        }
+        for [Less, Equal, Greater].each |&o| {
+            t(Less, o, Less);
+            t(Equal, o, o);
+            t(Greater, o, Greater);
+         }
+    }
 }