On Jul 10, 2005, at 8:50 AM, David Abrahams wrote:
Douglas Gregor <doug.gregor@gmail.com> writes:
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?
No, color_map can be any property map from vertices to color values. We just tend to build them as vectors because it's a convenient storage mechanism.
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?
There's a little more overhead to a vector_property_map than an iterator_property_map<vector iterator, ...>, because the vector_property_map goes through a shared_ptr. I don't know if it has a measurable effect. Doug