-extern vertex_t *new_vertex(void);
-extern void free_vertex(vertex_t *);
-extern void vertex_add(vertex_t *);
-extern void vertex_del(vertex_t *);
-extern vertex_t *lookup_vertex(struct node_t *, struct node_t *);
+extern edge_t *new_edge(void);
+extern void free_edge(edge_t *);
+extern void edge_add(edge_t *);
+extern void edge_del(edge_t *);
+extern edge_t *lookup_edge(struct node_t *, struct node_t *);