Add FromIterator impl (#23)

Co-authored-by: Mitchell Berendhuysen <[email protected]>

src/default_btree.rs

@@ -790,6 +790,20 @@ where
     }
 }
 
+impl<K, V> FromIterator<(K, V)> for DefaultBTreeMap<K, V>
+where
+    K: Ord,
+    V: Default,
+{
+    fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self {
+        let mut map = DefaultBTreeMap::default();
+        for (k, v) in iter {
+            let _ = map.insert(k, v);
+        }
+        map
+    }
+}
+
 #[macro_export]
 /// A quick way to instantiate a BTreeMap.
 ///

src/default_hashmap.rs

@@ -651,6 +651,21 @@ where
     }
 }
 
+impl<K, V, S> FromIterator<(K, V)> for DefaultHashMap<K, V, S>
+where
+    K: Eq + Hash,
+    V: Default,
+    S: BuildHasher + Default,
+{
+    fn from_iter<T: IntoIterator<Item = (K, V)>>(iter: T) -> Self {
+        let mut map = DefaultHashMap::with_hasher(Default::default());
+        for (k, v) in iter {
+            let _ = map.insert(k, v);
+        }
+        map
+    }
+}
+
 #[macro_export]
 /// A quick way to instantiate a HashMap.
 ///

tests/test_btree.rs

@@ -700,3 +700,13 @@ fn macro_test_slight_change_btree() {
     assert_eq!(map, _map);
     assert_eq!(map1, _map1);
 }
+
+#[test]
+fn from_iter_btreemap() {
+    let data = [(1, 1), (2, 2), (3, 3), (4, 4)];
+    let map: DefaultBTreeMap<i8, u8> = data.iter().cloned().collect();
+
+    let correct_map: DefaultBTreeMap<i8, u8> = defaultbtreemap!((1, 1), (2, 2), (3, 3), (4, 4));
+
+    assert_eq!(map, correct_map);
+}

tests/test_hashmap.rs

@@ -362,6 +362,16 @@ fn into_iter_default_hashmap() {
     assert_eq!(v, correct_v);
 }
 
+#[test]
+fn from_iter_hashmap() {
+    let data = [(1, 1), (2, 2), (3, 3), (4, 4)];
+    let map: DefaultHashMap<i8, u8> = data.iter().cloned().collect();
+
+    let correct_map: DefaultHashMap<i8, u8> = defaulthashmap!((1, 1), (2, 2), (3, 3), (4, 4));
+
+    assert_eq!(map, correct_map);
+}
+
 #[test]
 fn borrow_loop_over_default_hashmap() {
     let mut map: DefaultHashMap<i8, u8> = DefaultHashMap::new();