Add VertexMap to attach data to vertices

src/traits.rs

@@ -1,3 +1,5 @@
+use crate::maps::VertexMap;
+
 // TODO: Add functions to reserve memory for vertices and edges.
 // TODO: Add iterator of incident edges for a vertex.
 // TODO: Add finding incident vertices for an edge.
@@ -8,6 +10,8 @@ pub trait GraphTopology {
 
     fn vertex_count(&self) -> usize;
     fn edge_count(&self) -> usize;
+    fn vertex_capacity(&self) -> usize;
+    fn vertex_map<T: Clone>(&self, default: T) -> VertexMap<Self::Vertex, T>;
     fn degree(&self, v: Self::Vertex) -> usize;
     fn are_adjacent(&self, v1: Self::Vertex, v2: Self::Vertex) -> bool;
     fn vertices(&self) -> impl Iterator<Item = Self::Vertex>;