diff options
| -rw-r--r-- | src/libstd/hashmap.rs | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/src/libstd/hashmap.rs b/src/libstd/hashmap.rs index 3221ff4730d..fb4cab72126 100644 --- a/src/libstd/hashmap.rs +++ b/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)) { @@ -759,6 +767,13 @@ mod test_map { } #[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(); assert!(m.insert(1, 2)); |