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

Subject: Re: [Boost-users] [boost] Create Graph in Function
From: Jeremiah Willcock (jewillco_at_[hidden])
Date: 2009-10-28 22:02:45

On Wed, 28 Oct 2009, Sandeep Gupta wrote:

> 
> 
> On Wed, Oct 28, 2009 at 6:12 PM, James Thunes <j.thunes_at_[hidden]> 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<vecS, vecS, bidirectionalS, no_property, EdgeProperty> Graph;
>
>       Thank you for any help you can give,
>       James
>
>       Try shared_ptr. Something like.
>
>
>   function(){
>    typedef  adjacency_list<vecS, vecS, bidirectionalS, no_property, EdgeProperty>  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