Re: [Boost-users] How to get a graph that does not accept parallel edges?

Hi Eric, 2006/9/8, Eric Fowler :

How do I declare a graph that does not allow parallel edges? I have come up with this but IMO it is sort of, well, kludgey:

typedef adjacency_list Graph;

This works because std::set does not like multiple entries.

Quoting adjacency_list documentation: "One of the first things to consider when choosing the OutEdgeList is whether you want adjacency_list to enforce the absence of parallel edges in the graph (that is, enforce that the graph not become a multi-graph). If you want this enforced then use the setS or hash_setS selectors. If you want to represent a multi-graph, or know that you will not be inserting parallel edges into the graph, then choose one of the Sequence types: vecS, listS, or slistS."

But what if for performance reasons (say) I want a listS or vecS instead of setS?

To me it looks like there is no special check inside adjacency_list for parallel edges. The check is only done through the underlying container. So if you want to use listS or vecS as an outedge-container, you have to check for parallel edges yourself.

In adjacency_list.hpp I find: template <> struct parallel_edge_traits<setS> { typedef disallow_parallel_edge_tag type; };

Which suggest the existence of a more elegant mechanism. Anybody know what that is?

For me, this validates the above assumption. This tag is set through specializing on the OutEdgeList container. HTH, Stephan