On Thu, 29 Dec 2011, Kelvin Chung wrote:
On 2011-12-29 15:00:10 +0000, Nicholas Mario Wardhana said:
On 29 December 2011 15:16, Kelvin Chung <kelvSYC@mac.com> wrote:
Suppose I have the following:
template <class T> class Graph { // Adapter class that I use for my purposes typedef typename boost::adjacency_list<boost::vecS, boost::vecS, boost::directedS, T> innerGraph; typedef typename boost::graph_traits<innerGraph>::vertex_descriptor VertexDescriptor;
innerGraph G; public: void addVertex(const T& vertex); bool containsVertex(const T& vertex) const;
void addEdge(const T& from, const T& to); // More stuff here };
The intent of this adapter class is to basically abstract out all the mentions of stuff like the descriptors and such. So a good helper function to this end would be a function that retrieves the VertexDescriptor for a given T, if it exists. Is there such a function already in the BGL, or do I have to manage that separately (ie. having an external map)?
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How about storing the descriptor in the T object, by having a member like
VertexDescriptor descriptor;
?
Constant-time retrieval is guaranteed, but then you have to typedef VertexDescriptor in your T. Alternatively, you can have it globally defined.
Wouldn't that impose a concept (or interface) requirement on T? (BTW, what are the current concept requirements for T? Does changing the second template param to boost::setS to disallow parallel edges also implies that T must be less-than comparable?) Or at least, present a chicken-and-egg problem regarding putting my T in a wrapper that also stores the VertexDescriptor? (Not that keeping an external T to VertexDescriptor map is any different, mind you, but at least I know what the external map means for the concept/interface requirements for T.)
You can use the adjacency_list_traits class (documented in the adjacency_list documentation) to get the descriptor types to use in your bundled property type.
(Sometimes the language of the BGL documentation confuses me. Especially the fact that "Bundled Properties" seems to be a euphemism of "use a data structure that you like")
That is exactly what it is for -- using your own data structure for properties. -- Jeremiah Willcock