Re: [boost] [Graphs] visitors

From: David Abrahams (abrahams_at_[hidden])
Date: 2000-09-08 16:29:24

From: <jsiek_at_[hidden]>

> This approach has the advantage that the same functor, say
> predecessor_recorder, could be used with different algorithms
> at different event points.
>
> dijkstra_shortest_paths(...,
>   make_pair(make_pair(record_predecessors(p), explore_edge_tag()),
>             null_visitor())
>   );
>
> bellman_ford_shortest_paths(...,
>   make_pair(make_pair(record_predecessors(p), relax_tag()),
>             null_visitor())
>   );
>

I like where you're going with this. Usage-wise, the prevalence of make_pair
here puts me off a bit. Would it be possible to do something like what we've
done in operators.hpp to determine whether a pair's SecondType is a tag?
Then maybe we could write

 dijkstra_shortest_paths(...,
   make_pair(record_predecessors(p), explore_edge_tag())
   );

In fact, it would be nicest to write

 dijkstra_shortest_paths(...,
   record_predecessors(p, explore_edge_tag())
   );

Also, I would rename these tag types "on_..." instead of "..._tag", e.g.
"on_explore_edge()".

-Dave