Re: [Boost-users] [boost] Create Graph in Function

Jeremiah Willcock wrote:

On Wed, 28 Oct 2009, Sandeep Gupta wrote:

...

On Wed, Oct 28, 2009 at 6:12 PM, James Thunes wrote: 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 Graph;

Thank you for any help you can give, James

Try shared_ptr. Something like.

function(){ typedef adjacency_list Graph; shared_ptr< Graph > gptr( new Graph(n) ); return gptr; }

You could also just declare the graph in whichever scope will end up storing it and then pass it by reference to the construction function:

void function(Graph& g) { // build g, or build a temporary and assign it to g }

Graph the_graph; function(the_graph);

Where are you going to be putting the final graph? Will it be in a variable in your main(), even if it is not constructed there?

-- Jeremiah Willcock Jeremiah,

I'm sorry if I was not clear in my first post. The majority of the code (along with the main routine) is written in Fortran. I am using the graph to update a number of arrays which are needed for this Fortran code. I will create the graph in a subroutine (or c++ function) and modify it in another c++ function. The graph is not called in the main routine, only in subroutines. I need to know the way the graph is stored so I can pass it back to the main function (or perhaps define it as a public variable). In reference to the code snippet above, am I correct in reading it as the creating routine will be defined as: void function(Graph& g) { // build g, or build a temporary and assign it to g } and then the function to modify it would be defined as: void modify_the_graph(Graph& g){ \\ some graph manipulations here } -James Thunes