On Wed, 28 Oct 2009, James wrote:

That is the issue.  I agree that to manipulate the graph in the Fortran portion of the code would be difficult (due the lack of a comparable data type).  Luckily, I don't need to modify the graph in the Fortran portion of the code, I just need to allow for a c++ function to access the graph.  If I can define the graph as a global variable in c++ and negate the need to pass the graph from the create_graph function to the modify_graph function via the Fortran main routine:
 Create_Graph.cpp -> Main.f -> Modify_Graph.cpp
would be great.

Would I accomplish this as:
in create_graph.cpp
Graph& g;

void create_graph(){
\\ create graph
}

and in modify_graph.cpp
extern Graph& g;

void modify_graph(){
\\...
}

The storage for the graph needs to be somewhere; making the variables of type Graph rather than Graph& would solve that problem.

-- Jeremiah Willcock