---

yaml
---
r: 65522
b: refs/heads/master
c: 75f1b7f
h: refs/heads/master
v: v3

Author: lilyball

[refs]

@@ -1,5 +1,5 @@
 ---
-refs/heads/master: 7bc950c43c820b0a0cfeede7dcf2d719625dbd90
+refs/heads/master: 75f1b7f96fa4e91244a96ba92f615f3213d97519
 refs/heads/snap-stage1: e33de59e47c5076a89eadeb38f4934f58a3618a6
 refs/heads/snap-stage3: 18e3db7392d2d0697b7e27d6d986139960144d85
 refs/heads/try: 7b78b52e602bb3ea8174f9b2006bff3315f03ef9

trunk/src/libstd/hashmap.rs

@@ -467,6 +467,14 @@ impl<K: Hash + Eq, V> HashMap<K, V> {
         self.mangle(k, (), |k,_a| f(k), |_k,_v,_a| ())
     }
 
+    /// Insert a key-value pair into the map if the key is not already present.
+    /// Otherwise, modify the existing value for the key.
+    /// Returns the new or modified value for the key.
+    pub fn insert_or_update_with<'a>(&'a mut self, k: K, v: V,
+                                     f: &fn(&K, &mut V)) -> &'a mut V {
+        self.mangle(k, v, |_k,a| a, |k,v,_a| f(k,v))
+    }
+
     /// Calls a function on each element of a hash map, destroying the hash
     /// map in the process.
     pub fn consume(&mut self, f: &fn(K, V)) {
@@ -758,6 +766,13 @@ mod test_map {
         assert_eq!(*m.find_or_insert_with(1, |_| 3), 2);
     }
 
+    #[test]
+    fn test_insert_or_update_with() {
+        let mut m = HashMap::new::<int, int>();
+        assert_eq!(*m.insert_or_update_with(1, 2, |_,x| *x+=1), 2);
+        assert_eq!(*m.insert_or_update_with(1, 2, |_,x| *x+=1), 3);
+    }
+
     #[test]
     fn test_consume() {
         let mut m = HashMap::new();