Add GraphTopology::incident_edges() and tests

src/models/append_graph.rs

@@ -130,6 +130,14 @@ impl GraphTopology for AppendGraph {
         (0..self.incidences.len()).step_by(2).map(Incidence)
     }
 
+    fn incident_edges(&self, v: Self::Vertex) -> impl Iterator<Item = Self::Edge> {
+        RawIncidenceIterator {
+            graph: self,
+            incidence: self.vertices[v.0].first_incidence,
+        }
+        .map(|(_, e)| e.normalize())
+    }
+
     fn incidences(&self, v: Self::Vertex) -> impl Iterator<Item = (Self::Vertex, Self::Edge)> {
         RawIncidenceIterator {
             graph: self,

src/models/graph.rs

@@ -200,6 +200,10 @@ impl GraphTopology for Graph {
             .map(|(i, _)| i)
     }
 
+    fn incident_edges(&self, v: Self::Vertex) -> impl Iterator<Item = Self::Edge> {
+        self.raw_incidences(v).map(|(_, e)| self.normalize_edge(e))
+    }
+
     fn incidences(&self, v: Self::Vertex) -> impl Iterator<Item = (Self::Vertex, Self::Edge)> {
         self.raw_incidences(v)
             .map(|(vs, e)| (self.vertices.get_idx(vs.0).unwrap(), self.normalize_edge(e)))