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