Douglas Gregor <doug.gregor@gmail.com> writes:
On Jul 9, 2005, at 10:38 PM, David Abrahams wrote:
Douglas Gregor <doug.gregor@gmail.com> writes:
color_map has a nontrivial default of: vector_property_map<color_type, typeof(index_map)>
Say, that doesn't correspond to what I see at http://www.boost-consulting.com/boost/libs/graph/doc/ depth_first_search.html and furthermore I think that last "nontrivial default" is a type, not a value. Can you clear this up? Did you mean a different algorithm?
I changed two things, to try to simplify the example:
Hmm, but any real simplification tends to confuse if the reader does what I did, and refers to the BGL docs. Anyway, suppose I want to use your simplified example. What is the *value* of the last "nontrivial default?" You wrote: vector_property_map<color_type, typeof(index_map)> but as I said, that seems to be a type!
1) I dropped the optional root_vertex parameter.
Okay.
2) I changed the default for the color_map to something a little simpler.
And impossible ;-)
The real color map will be built like this:
typename graph_traits<Graph>::vertices_size_type n = num_vertices(graph); std::vector<default_color_type> color_vec(n); iterator_property_map< typename std::vector<default_color_type>::iterator, IndexMap
default_color_map(color_vec.begin(), index_map);
The really tough part is that color_vec needs to stick around, so it can't be buried in a function object somewhere.
Well, you can have it in a function object, as long as there's a way to retrieve it, or the function object outlives the function call. But more to the point, shouldn't it be part of the color_map itself? There's no rule that the color_map has to be a simple vector, is there?
An equivalent (but slightly simpler) alternative is to use:
typename graph_traits<Graph>::vertices_size_type n = num_vertices(graph); vector_property_map<default_color_type, IndexMap>(n, index_map);
Yes, that looks simpler, because it avoids the issue of holding onto a separate color_vec. Is there some downside? -- Dave Abrahams Boost Consulting www.boost-consulting.com