From 55bd6cee2ff9123c68d7361e235ac99927f4b062 Mon Sep 17 00:00:00 2001
From: Tim Chevalier <chevalier@alum.wellesley.edu>
Date: Thu, 6 Sep 2012 12:11:48 -0700
Subject: [PATCH] Test that merge sort is stable -- thanks to Jesse Jones

Closes #3399
---
 src/libstd/sort.rs | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/libstd/sort.rs b/src/libstd/sort.rs
index 4c10e274d49..64ea19d35f9 100644
--- a/src/libstd/sort.rs
+++ b/src/libstd/sort.rs
@@ -307,6 +307,28 @@ mod tests {
         let v2 = merge_sort(le, v1);
         assert v2 == ~[1, 2, 3];
     }
+
+    #[test]
+    fn test_merge_sort_stability()
+    {
+        // tjc: funny that we have to use parens
+        pure fn ile(x: &(&static/str), y: &(&static/str)) -> bool
+        {
+            unchecked            // to_lower is not pure...
+            {
+                let x = x.to_lower();
+                let y = y.to_lower();
+                x <= y
+            }
+        }
+
+        let names1 = ~["joe bob", "Joe Bob", "Jack Brown", "JOE Bob",
+                       "Sally Mae", "JOE BOB", "Alex Andy"];
+        let names2 = ~["Alex Andy", "Jack Brown", "joe bob", "Joe Bob",
+                       "JOE Bob", "JOE BOB", "Sally Mae"];
+        let names3 = merge_sort(ile, names1);
+        assert names3 == names2;
+    }
 }
 
 // Local Variables: