Replace VertexMap/EdgeMap.len with capacity

Rename EdgeMap.len to capacity.
Add VertexMap.capacity and EdgeMap.capacity.
Deprecate VertexMap.len and EdgeMap.len.

src/testing/maps_testing.rs

@@ -53,16 +53,16 @@ macro_rules! vertex_map_tests {
             let mut graph = <$T>::new();
             graph.add_vertex();
             let mut map = graph.vertex_map(42);
-            let initial_len = map.len();
-            while graph.vertex_capacity() <= initial_len {
+            let capacity_before = map.capacity();
+            while graph.vertex_capacity() <= capacity_before {
                 graph.add_vertex();
             }
             assert!(
-                map.len() < graph.vertex_capacity(),
+                map.capacity() < graph.vertex_capacity(),
                 "precondition: map is stale before sync"
             );
             map.sync(&graph);
-            assert_eq!(map.len(), graph.vertex_capacity());
+            assert_eq!(map.capacity(), graph.vertex_capacity());
         }
 
         #[test]
@@ -109,7 +109,7 @@ macro_rules! vertex_map_deletion_tests {
             let capacity_before = graph.vertex_capacity();
             graph.delete_vertex(v2);
             map.sync(&graph);
-            assert_eq!(map.len(), capacity_before);
+            assert_eq!(map.capacity(), capacity_before);
             assert_eq!(map[v1], 5);
         }
 
@@ -197,16 +197,16 @@ macro_rules! edge_map_tests {
             let v2 = graph.add_vertex();
             graph.add_edge(v1, v2);
             let mut map = graph.edge_map(42);
-            let initial_len = map.len();
-            while graph.edge_capacity() <= initial_len {
+            let capacity_before = map.capacity();
+            while graph.edge_capacity() <= capacity_before {
                 graph.add_edge(v1, v2);
             }
             assert!(
-                map.len() < graph.edge_capacity(),
+                map.capacity() < graph.edge_capacity(),
                 "precondition: map is stale before sync"
             );
             map.sync(&graph);
-            assert_eq!(map.len(), graph.edge_capacity());
+            assert_eq!(map.capacity(), graph.edge_capacity());
         }
 
         #[test]
@@ -259,7 +259,7 @@ macro_rules! edge_map_deletion_tests {
             let capacity_before = graph.edge_capacity();
             graph.delete_edge(e2);
             map.sync(&graph);
-            assert_eq!(map.len(), capacity_before);
+            assert_eq!(map.capacity(), capacity_before);
             assert_eq!(map[e1], 5);
         }