[Boost-users] [BGL] how does automatic vertex_index creation work?

Hi folks! I defined a customary graph type which always uses integers in a bound range to adress the vertices. It is therefore as if one would use an adjacency_list with vecS as vertex storage set. Since I want to run an algorithm requiring a vertex_index property to be present on my custom graph, I was looking at the code of the adjacency_list graph. The docs say, that somewhere in the code the vertex_index map does get created automatically if the vertex set is vecS, but where and how is it done? The code is just too big or too advanced for me to find the appropiate lines. Could someone please enlighten me? Thanks in advance, Sebastian Weber