Update IncidenceCursor trait doc with note on Copy

len() is generally expected to describe the number of elements in a collection,
but in this case elements beyond len() are accessible without restriction.
capacity() is a better name because it describes data storage size.

src/lib.rs

@@ -133,7 +133,7 @@ pub mod models;
 pub mod traits;
 
 pub mod prelude {
-    pub use crate::traits::{GraphTopology, GraphTopologyDeletion};
+    pub use crate::traits::{GraphTopology, GraphTopologyDeletion, IncidenceCursor};
 }
 
 mod testing;

src/maps.rs

@@ -18,11 +18,6 @@ impl<V: Copy, T: Clone> VertexMap<V, T> {
         self.inner.capacity()
     }
 
-    #[deprecated(since = "0.2.2", note = "use 'capacity' instead")]
-    pub fn len(&self) -> usize {
-        self.capacity()
-    }
-
     pub fn sync<G: GraphTopology<Vertex = V>>(&mut self, graph: &G) {
         self.inner.resize(graph.vertex_capacity());
     }
@@ -58,11 +53,6 @@ impl<E: Copy, T: Clone> EdgeMap<E, T> {
         self.inner.capacity()
     }
 
-    #[deprecated(since = "0.2.2", note = "use 'capacity' instead")]
-    pub fn len(&self) -> usize {
-        self.capacity()
-    }
-
     pub fn sync<G: GraphTopology<Edge = E>>(&mut self, graph: &G) {
         self.inner.resize(graph.edge_capacity());
     }

src/models/append_graph.rs

@@ -91,7 +91,7 @@ impl GraphTopology for AppendGraph {
     }
 
     fn vertex_capacity(&self) -> usize {
-        self.vertices.len()
+        self.vertices.capacity()
     }
 
     fn vertex_map<T: Clone>(&self, default: T) -> VertexMap<Self::Vertex, T> {

src/traits.rs

@@ -38,7 +38,7 @@ pub trait GraphTopology {
     /// when an algorithm needs to pause traversal, perform other graph queries or mutations, and
     /// then continue from where it left off. This cursor type can be obtained via
     /// [`incidence_cursor`](Self::incidence_cursor).
-    type IncidenceCursor: IncidenceCursor<Self> + Copy;
+    type IncidenceCursor: IncidenceCursor<Self>;
 
     /// Returns the number of vertices in the graph.
     fn vertex_count(&self) -> usize;
@@ -210,10 +210,13 @@ pub trait GraphTopologyDeletion: GraphTopology {
 
 /// A cursor for traversing the incidences of a vertex one step at a time.
 ///
+/// Because the cursor is [`Copy`], its state can be saved and restored to replay or branch a
+/// traversal.
+///
 /// Cursors are obtained via [`GraphTopology::incidence_cursor`]. See
 /// [`GraphTopology::IncidenceCursor`] for guidance on when to prefer a cursor over
 /// [`GraphTopology::incidences`].
-pub trait IncidenceCursor<G: GraphTopology + ?Sized> {
+pub trait IncidenceCursor<G: GraphTopology + ?Sized>: Copy {
     /// Advances the cursor and returns the next incidence as `Some((u, e))`, or `None` if the
     /// traversal is exhausted.
     ///
@@ -222,7 +225,6 @@ pub trait IncidenceCursor<G: GraphTopology + ?Sized> {
     /// ```
     /// # use grapherity::prelude::*;
     /// # use grapherity::models::Graph;
-    /// # use grapherity::traits::IncidenceCursor;
     /// // Constructs a graph with two vertices connected to `v`.
     /// let mut graph = Graph::new();
     /// let v = graph.add_vertex();