Re: [Boost-users] Info about a graph with structure instead node

From: Doug Gregor (dgregor_at_[hidden])
Date: 2004-07-14 09:39:03

On Jul 12, 2004, at 3:36 AM, Daniele Carlucci wrote:

> Hi all,
> I'm a newby in this library. I'm interested to make a graph of 
> network. It's possible or is very hard to make?
> I want to have inside every node a struct.

Anything is possible with the BGL :) This particular thing is too hard 
to do at the moment, but will become much easier as soon as we release 
1.32.0 (in about 2 weeks):

First step is to create a property tag for your struct:

   enum vertex_mystruct_t { vertex_mystruct };

Now make that tag a full-fledged graph property tag:

   namespace boost {
     BOOST_INSTALL_PROPERTY(vertex, mystruct);
   }

Now when you create your graph type, you can store a value of any type 
X along with each vertex like this (the first three parameters can be 
anything, of course):

   struct X { int foo; };

   typedef adjacency_list<listS, vecS, bidirectionalS, 
property<vertex_mystruct_t, X> > Graph;
   Graph g; // creating a graph instance

To actually get at the X values for each vertex, we need to grab the 
property map:

   property_map<vertex_mystruct_t, Graph>::type 
X_map(get(vertex_mystruct, g));

Now, finally, we can get to the X structure for any vertex_descriptor v:

   X_map[v].foo = 17;

In 1.32.0, the BGL will support "bundled properties", which means that 
this whole e-mail would boil down to:

   typedef adjacency_list<listS, vecS, bidirectionalS, X> Graph;
   Graph g;
   graph_traits<Graph>::vertex_descriptor v = ...;
   g[v].foo = 17;

        Doug