If you think about it, an object **is** a node in a graph, and its instance variables
are the arcs!  Just as LISP is based on list nodes, OOPLs are based on tree nodes.
In fact, the phrase "object **graph**" is in common use.

Of course, a "TreeNode" or "GraphNode" class still has value: it provides both
a standard interface/protocol for graph navigation (e.g., what message does one
send to get all the arcs (or all the children) of a node), and also a home for
graph-theoretic algorithms (e.g, topological sort).

--Alan

Jerome Garcia wrote:

>      I have not been able to find a generic node class in Squeak. Does
>      Squeak provide a node class similar to the TreeNode class provided by
>      Dolphin Smalltalk? If not, is there a reason why it should not?
>
>      Jerome E. Garcia
>      jegarcia at adventurousmind.com