Perhaps an easy answer, but I am working on adding a boost graph to an existing code. I would like to create the graph in a function (not main) and then read/modify it in a separate function. I am unsure as to what I need to pass between the functions to allow this to work.

In other words, I am able to correctly create the graph in a function and modify as necessary. This function will be called many times as the code runs and it is inefficient to recreate the graph every time. I want to create the graph once when the code is run and pass the created graph to the function.

Due to the structure of the code (mostly Fortran), I can not define the graph in the main function of the code.

My graph is defined as:
adjacency_list<vecS, vecS, bidirectionalS, no_property, EdgeProperty> Graph;

Thank you for any help you can give,
James