[boost] [BGL/PM] Composition of two property maps

Subject: [boost] [BGL/PM] Composition of two property maps
From: Matthias Walter (xammy_at_[hidden])
Date: 2010-02-16 07:30:13

Hi,

I currently have a function which gets a graph plus an index-map and
want's to call a BFS. Therefore it needs to build a color-map which maps
vertex_descriptors to colors. As the user already gives a way to map
vertex_descriptor to index, I'd like to use this mapping. What I need is
a way to define a property map as a composition:

composed-map (vertex_descriptor) ->  color

via

color-map (index-map (vertex_descriptor)) -> color

whereas index-map (vertex_descriptor) -> index and color-map (index) ->
color

Of course this should not be too difficult to implement, so I'd just
like to ask whether there already exists some kind of implementation,
because I neither found a hint by looking in the docs, nor by digging
through some of the code.

The actual reason I ask is because there might be other ways to come
around the problem, e.g. making the color-map itself use
vertex_descriptors as keys, so maybe my suggested solution is not the best.

best regards
Matthias Walter