Re: [Boost-users] boost.graph question concerning edge descriptor details

On Aug 23, 2004, at 11:30 AM, Jeff Holle wrote:

I may have answered my own question. The Compare functor that does the trick is: struct ltExternalEdge : public std::binary_function { bool operator()(const ExternalEdge& __x, const ExternalEdge& __y) const { return (__x.first < __y.first || (!(__y.first < __x.first) && __x.second.get_property() < __y.second.get_property())) ? true : false; } };

Is such a Compare operator safe? Note that I'm note using internal properties.

This is not guaranteed to work, because edge descriptors aren't required to have the "get_property" or "first" members. Practically speaking, I think it will work, but can't be sure.

It would be really nice if the object that edge_iterator references implemenented a operator< method. Then it would work seamlessly with the std::pair operator< method, which I pretty much copied in the above code.

I'm not sure that this can always be implemented efficiently, but it surely would be useful. Doug