Re: [Boost-users] BGL: EdgeIterator construction of graphs

From: Doug Gregor (dgregor_at_[hidden])
Date: 2005-07-22 11:46:54

Hi Sebastian,

On Jul 22, 2005, at 7:57 AM, Sebastian Weber wrote:
> I'm trying to initialize my adjacency_list graph via an EdgeIterator.
> Since I do not want parallel edges to be present in my graph, but still
> use vecS as EdgeList-storage because of memory considerations, my
> EdgeIterator needs somehow a reference to the graph under construction.
> Some code might explain it better:
>
> typedef boost::adjacency_list<boost::vecS, boost::vecS,
> boost::undirectedS > graph_t;
> typedef boost::my_edge_iterator<base_rand_gen_t, graph_t> SFGen;
>
> graph_t bg = graph_t(SFGen(bg, base_rand, 100), SFGen(), 100);
>
> This code compiles fine, but seg-faults immediatly since bg does not
> seem to be defined when my iterator gets constructed.

My gut feeling is that this should work.. you're not trying to make a 
copy of "bg" when you builf SFGen, right? SFGen needs to store a 
pointer to a graph_t, not a reference or copy.

>  A solution would
> be to provide a add_edge_range-function which gets as input the
> EdgeIterator and the corresponding empty boost graph.

Good idea.

> This function
> would then build up the graph or is there a better way to do this?

Nothing better than making lots of add_edge calls, which is exactly 
what the EdgeIterator constructor does.

        Doug