These graph traversal functions are analogous to the `Accept`
member function of the container class (see Section ).
Each of these functions takes a reference to a `Visitor`
and performs a traversal.
I.e., all the *vertices* of the graph are visited systematically.
When a vertex is visited, the `Visit` function of the visitor
is applied to that vertex.

`DepthFirstTraversal`and`BreadthFirstTraversal`-
Both of these functions accept two arguments--a reference to a
`Visitor`and a reference to a vertex. The vertex specifies the starting node for either a depth-first traversal or a breadth-first traversal of the graph. `TopologicalOrderTraversal`-
A topological sort is an ordering of the nodes of a directed graph.
This traversal visits the nodes of a directed graph in the order
specified by a topological sort.
Therefore, it is a member function of the
`Digraph`class.

Copyright © 1997 by Bruno R. Preiss, P.Eng. All rights reserved.